Measuring the hot spell of June 2017

The last week has seen high temperatures across large parts of England and Wales in what has been the longest continuous hot spell in June since the hot, dry summer of 1976. Temperatures of 30°C or more were recorded somewhere across England and Wales for the last five days, peaking on Wednesday 21 June at 34.5°C at Heathrow, London which was the hottest day of the year so far. However, for Scotland and Northern Ireland it was hotter on 26 May (Lossiemouth, Moray, 29.4°C and Castlederg, Tyrone, 26.2°C)

Below is a rundown of the top temperatures recorded in each of the home nations through this hot spell:

Location Date Temperature / °C
Heathrow, London 21 June 34.5
Cardiff, South Glamorgan 21 June 31.0
Floors Castle, Roxburghshire 18 June 26.5
Helen’s Bay 18 June 25.6

Although notable, this hot spell didn’t break any national temperature records, it was for many of the long running weather stations the hottest June day since the 1976 heatwave. One exception was that on Monday 19 June, Newport in Shropshire recorded a temperature of 30.8°C which narrowly beat the previous record of 30.7°C from 29 June 1976 in an 85 year record.

The images below show how the pattern of heat altered over the course of this period. With high pressure dominating, bringing a warm south or southwesterly flow of air, heat was concentrated across southern parts of the UK, but temperatures in the north of England and Wales were in the high 20°C’s over last weekend and the early part of this week.

Maximum temperatures June 2017

Many sites recorded their highest June maximum temperatures since 1976 this week. However the hot spell in June 1976 remains the UK’s most significant for the month when temperatures exceeded 32°C widely across England and the current UK maximum temperature record for June was set at Mayflower Park, Southampton on 28 June when 35.6°C was recorded. The maps below show the extent and longevity of the heat over that period.

Maximum temperatures June 1976

The Met Office are responsible for maintaining the network of observing sites across the UK and their readings play an important first step in helping meteorologists to forecast the weather. Our weather station sites are selected to ensure that the observations are representative of the wider area around the station and not disproportionately affected by local effects. This means that weather stations in urban areas, although carefully sited to be representative of that area, will always be warmer than surrounding rural locations, but still reflect the conditions being experienced by people living and working there.

The map below shows the temperature measurements which were recorded by people contributing to our Weather Observations Website (WOW) alongside the Met Office official observations on the afternoon of the 21 June.

WOW observations 21 June 2017

The Met Office sites recorded maximum temperatures from 32.9 °C at London, St James’ Park to 33.8 °C  at Kew Gardens and 34.5 °C at London Heathrow a range of 1.6 °C. The WOW readings clearly show a much larger range and the importance of having a well-sited thermometer which isn’t in full sun or in a very sheltered location to provide observations that are representative of the wider area. However, the WOW data are very useful to add context and show that some people may experience temperatures higher or lower than the official observations around their home or workplace.

If you’d like to find out more about contributing to WOW you can sign up or enter an observation here.

More information about this hot spell of weather is availble on our UK climate pages.

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Could navigational buoys help with Met Office forecasts?

For the first time the Met Office has set up a trial to see if it is possible to use navigational buoys to gather weather data from near coastal areas.

The Met Office has just 10 weather observation buoys around the UK coast, meaning this area, which is vital when it comes to the understanding of weather systems transitioning from the open ocean to the land, is particularly data sparse.

Trinity House buoys around the coast of England and Wales

Trinity House, the lighthouse authority for England, Wales, the Channel Islands and Gibraltar, joined forces with the Met Office to help look at ways to get the latest weather information to ships of 300 tonnes or more.

Met Office weather stations are already placed on Trinity House’s Lightvessels* in the English Channel. Anyone who’s heard the shipping forecast may well have heard Lightvessels mentioned as their readings are regularly used.  Trinity House also has over 400 navigation buoys around the coast.

Barrow 6 Buoy

The joint project looked at placing weather observation equipment on one of the existing navigation buoys and transmitting that data to the Met Office as another source of coastal observations.

Location of Barrow 6 in relation to our closest stations

A buoy in the Thames Estuary, Barrow 6, and  another in the Bristol Channel,  have now been equipped with wind, temperature, humidity, barometric pressure and sea surface temperature sensors.

AWS system being put onto Barrow 6

This is a similar set of sensors to the other buoys in the Met Office network, although it uses  a different set up, so the systems can easily be installed on a third party buoy. In the future the data from the buoy will hopefully not only be sent to the Met Office but also to ships via Automatic Identification System (AIS**).

This new project opens up the possibility of increasing observations from this data sparse marine location.

*Lightvessel – ships that act as light houses out at sea.

**AIS is a VHF network of transceivers on ships of 300 tonnes or more which aids navigation. It is primarily an anti collision system but has dedicated message formats for other data, including meteorological data.

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Heavy rain boosts rainfall totals for Southern England

The mid-month statistics for May (1-17 May) show the month got off to a dry start, although the heavy rain yesterday brought up rainfall totals in some areas. It has also been a sunny and moderately mild early May for many.

The anticyclonic theme that dominated the UK weather in April continued into the start of May, meaning in some regions there was little rainfall aside from the rain on Wednesday. East Anglia and most of Scotland have been particularly dry so far this month, with only around 10% of the whole-month average up to 17 May. It has been wetter towards the south-west and west, with some places in the Lake District and western Wales already approaching their monthly rainfall averages. From a national perspective, the UK has so far seen 44% of the whole-month average so far.

Following the heavy rainfall on 17 May, Dorset and Hampshire are now at 79% of their long term average for the whole of May. South Farnborough in Hampshire for example had only received 12.8mm of rain up to 15th May, just 24% of the monthly average. The rain over the past two days has pushed the total up to 52.2mm which is 99.7% of the site’s average for the month. On average South Farnborough sees only 9 days in May with more than 1mm of rain recorded so it’s not that unusual for a large proportion of the monthly average to fall in a few notably wet days.

In contrast, Loch Glascarnoch in the Scottish highlands has so far this month received only 6.4 mm of rain, just 7% of its monthly average. Overall Scotland has so far received 19.5mm which is 23% of its average rainfall for May.

Temperatures for the month so far have been close to average from a UK perspective, with the mean temperature being just 0.2°C above the long term average. Northern Ireland has been the mildest region compared to its long term average with mean temperatures 1.1°C above the average so up to 17 May.

With the widely settled conditions, there were some rather chilly nights for the time of year with air frosts in certain areas. Ground frost was even observed in rural Devon on the morning of 10 May. Cloud-cover and high humidity meant an unusually warm night on 15/16 May with minima of 15 °C in places, and the highest temperature of the year so far was recorded at Gravesend in Kent with 25.8 °C on the 16th.

In line with the milder temperatures in Northern Ireland, sunshine hours have also been highest in this region. Northern Ireland has seen 92% its average monthly sunshine hours already this month with 168.2 hours. In contrast some eastern counties in England are some way below where you would expect them to be by this point in the month, with Suffolk and Norfolk recording 36 and 37% of their monthly average sunshine hours respectively. The UK as a whole has recorded 63% of its average monthly sunshine.

Provisional 1-17 May 2017 data Mean Temp Sunshine Hours Precipitation
Actual (°C) Diff to average Actual hours % of average Actual (mm) % of average
UK 10.6 0.2 116.5 63 30.5 44
England 11.2 0 94.6 50 33 57
Wales 10.9 0.3 120.1 64 50.2 58
Scotland 9.4 0.5 142.3 80 19.5 23
N. Ireland 11.3 1.1 168.2 92 38.5 53


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Early April statistics

Early provisional statistics for April (1st-26th) show that overall it has also been a sunny and warm month so far compared to the long-term 1981-2010 average.

Following on from the mid-month statistics, Middlesex remains the driest historical county with 2.7mm of rainfall so far this month just 6% of the long-term average for April which is 45mm. In comparison Sutherland has so far been the wettest historical county with 130.8mm of rain, 41% above the expected monthly rainfall.

The UK as a whole has seen just 41% of the average April rainfall; the wettest region has been Scotland with 62.5mm and the driest southern England with 8.1mm.

It is likely many of the rainfall statistics will change as we expect an area of low pressure to move in from the south-west over the Bank Holiday weekend. As a weather front pushes eastwards across the UK on Sunday and Monday, we could see 10-15mm of rain in some areas, especially in the south-west. Read more about this weekend’s weather in our latest news release.

Despite the recent low temperatures, with the coldest night reaching -6.2°C (Cromdale, Moray 18 April 2017), April has also so far been a warmer than average month. On 9 April 25.5°C was recorded at Cambridge, the warmest day of the year so far. Overall the UK mean temperature has so far been 0.6°C higher than the long-term average. The warmest area against its long-term average was in Scotland, with Forfarshire recording 1.1°C above its long-term monthly average.

Nearly all of the UK has already had the sunshine we would expect for the whole month, and there are still several days left to include in the statistics. Only Scotland and Northern Ireland are below the average with 88% and 63% respectively. The UK as a whole has already reached its monthly average with 148.4 hours of sunshine. The district with the most sunshine hours is the south east and central south of England with 188.3 hours of sunshine, 11% above the April average.

Early April Mean Temp Sunshine Hours Precipitation
1-26 2017 Actual Diff to average Actual hours % of average Actual % of average
UK 8C 0.6% 148.4 100 29.7mm 41%
England 8.8C 0.7% 169.9 110 11.9mm 20%
Wales 8.2C 0.6% 161.0 104 18.4mm 21%
Scotland 6.6C 0.5% 119.4 88 62.5mm 69%
N. Ireland 8.2C 0.6% 92.7 63 27.8mm 37%

You can keep up to date with the weather using our forecast pages and by following us on Twitter and Facebook, as well as using our new mobile app which is available for iPhone from the App store and for Android from the Google Play store.

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Big data – big challenge

The Met Office is facing new and increasing challenges because of the huge volume of data that we manage and produce. Alex Longden, who leads the team responsible for data provision for the data re-use community and private weather sectors, examines the situation in this blog.

The 335 million observations of data we store every day require huge computational capability. Our new supercomputer provides the processing power needed to manipulate the data in a timely and effective way. The complex numerical models developed by our scientists and meteorologists in turn create enormous data outputs, used for climate and weather prediction and by data users throughout the world to make weather outlooks more accurate than ever before.

The state of weather data infrastructure

The Met Office recognises that increases in observational and forecast data volumes have implications across both the public and private weather sectors. To understand this better, we recently partnered with the Open Data Institute, to carry out a review on ‘The state of weather data infrastructure’.

The review is encouraging discussion on how the global weather data infrastructure can be sustainable, and continue to deliver value to society, as well as looking at the need for continuing investment in technical infrastructure and supercomputing resources. It also looks at the role of global, regional and national meteorological services in collecting observations and generating forecasts.

In addition, the review highlights the technology creating new data and in turn generating new, big data challenges. Supercomputing is enabling new and improved weather models which are harnessing a variety of sources of weather observations from ground, air, sea and space based monitoring and sensors. These trends exist within a wider landscape of innovation and changing consumer expectations where instant and real-time access to data is increasingly essential.

We are striving towards making our data more openly accessible and useful to realise the social economic benefits brought by the new supercomputer, which delivers ever increasing accuracy yet exponential increases in data volumes that makes this more challenging.

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Early April remains dry but some rain is on the horizon

Preliminary mid-month statistics for April show the recent pattern of dry conditions has continued, particularly in the south, as high pressure has so far dominated the weather this month.

All regions in the UK, except northern Scotland, have so far experienced well under half of their average rainfall for the full month of April; the UK as a whole has had just over a quarter (26%) when compared with the average for the whole month (At the mid-month point you would normally expect to see around 57% of the full month average). The south of England has seen the least rainfall compared to its long-term average (1981–2010) with Middlesex being the historic county with the lowest rainfall volume: just 1mm.

Seven other English counties have seen only five per cent or less of the average rainfall for the whole of April so far: Berkshire, Buckinghamshire, Essex, Gloucestershire, Hertfordshire, Oxfordshire and Wiltshire. The wettest English historic county is Cumberland, where just over 20mm of rain has fallen so far this month, just over a quarter (26%) of the anticipated total for the month.

Northern Scotland is the only district with over half of its full-month average rainfall; it has received 63% of its April average so far.

Tim Legg, a climate scientist at the National Climate Information Centre, said: “The dry conditions for April so far follow a series of rather dry months through autumn and winter. For the UK as a whole it was the driest October-March period since 1995/96.”

Commenting on the dry weather, an Environment Agency spokesperson said: “Following a dry winter, some rivers, groundwaters and reservoirs are lower than normal for the time of year. We always advise that everyone use water wisely – especially during a period of dry weather – and to follow the advice of their water company should water saving measures be required. The Environment Agency, water companies, businesses and farmers are working together to minimise any potential impacts to people and the environment should the dry weather continue.”

There does look to be a break in the dry weather for the south by early next week as a stronger front looks likely to push southwards across the UK bringing the first meaningful rainfall to southern regions for around three weeks.

Alongside the low levels of precipitation, April has also seen above average sunshine hours so far with the UK already having seen 66% of its average sunshine by only halfway through the month. The sunniest region has been southern England which has had 121.1 hours of sunshine so far, three-quarters of its April average.

Mean temperatures are also above average, the UK being 1.1°C warmer than the long-term average. All regions and districts have been warmer than average with East Anglia experiencing a mean temperature 1.5°C above its long-term average.

Provisional 1-17 April 2017 data Mean temp (°C) Sunshine (hours) Rainfall (mm)
Actual  Diff from avg (°C) Actual % of avg Actual % of avg
UK 8.5 1.1 98.3 66 19.2 26
England 9.4 1.2 112.9 73 7.6 13
Wales 8.5 0.8 104.7 68 13.6 15
Scotland 7.1 1.0 78.9 58 40.2 44
N Ireland 8.4 0.8 61.8 42 17.7 24

You can keep up to date with the weather using our forecast pages and by following us on Twitter and Facebook, as well as using our new mobile app which is available for iPhone from the App store and for Android from the Google Play store.

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Are the next three months going to be scorching?

There are headlines in the media today suggesting the UK is in for “three months of sizzling weather”.  It would appear these stories have been based, in part, on the latest Met Office three month outlook for contingency planners.

This outlook is designed to help planners in business and Government assess the level of risk connected to different weather scenarios. It does not however identify weather for a particular day or week – so is not that useful when you want to know, for example, which summer weekend looks good for an outdoor event.

As discussed previously, the outlook is not a normal weather forecast. It’s an outlook based on probabilities which assesses the likelihood of five different scenarios for both temperature and rainfall for UK as a whole for the next three months. It is based on the more probable prevailing weather patterns and has to be used in the right context.

It’s a bit like the science-equivalent of factoring the odds on a horse race and like any horse race it’s always possible the favourite won’t win.  Users of the outlook are aware of the complexities and limitations of this type of forecast, and will include those factors in their decision making processes.

What does the current outlook for April-May-June 2017 say?

Signals from long-range prediction systems are relatively weak for the current 3 month period, consistent with a lack of large-scale global drivers. Overall, there is a slight increase in the likelihood of anticyclonic conditions. As a result of this, and the warmth being observed in many of the regions that act as sources for air travelling to the UK, there is an increased chance that the average temperature over April-May-June will be higher-than-normal.

However this far from implies the UK will predominantly experience warm, fine weather, and does not mean there can’t also be some colder spells. It is also important to remember that higher-than-average temperatures won’t necessarily feel like ‘good’ weather if it is also more cloudy, windy or wet than usual.

There is also a suggestion that drier-than-average conditions are slightly more likely than wetter-than-average but the signal is small and the likelihood of any extreme weather is close to normal during this period.

If you want a forecast for your area or are looking to plan up and coming activities head to our forecasts pages for a detailed 7 day forecast or a 30 day look ahead at weather trends.

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Why is forecasting low cloud so difficult?

You may have been enjoying the sun these past few days, and noticed that some website and app forecasts have been somewhat more pessimistic with their predictions of the cloud cover. But why is something as fundamental as cloudy or sunny actually so difficult to forecast?

As with most weather forecasting, computer models are relied upon to produce accurate simulations of the atmosphere to guide cloud-cover forecasts. Because computer resources are finite, the model cannot simulate all the small-scale detail present in the real world, but “sees” the world as a pixellated image. For UK forecasting, the pixel sizes are 1.5km in the horizontal and around 100m in the vertical at the typical altitude of low clouds. Therefore clouds at these scales, or smaller, are very difficult to represent. Their formation, evolution and dissipation is controlled by “parametrizations” – the part of the model used to deal with processes acting on a smaller scale than the pixel size.

Low cloud, or stratocumulus, is particularly difficult because it requires many different parametrizations to interact correctly with each other to produce an accurate forecast. Turbulence, which can both enhance the cloud by mixing moist air from below and destroy the cloud by mixing dry air from above, must interact with solar and thermal radiation, which can directly modify the cloud by heating or cooling the atmosphere, and indirectly modify it by altering the turbulence in a feedback process. These processes must also interact correctly with the light winds and slowly subsiding air typically associated with high-pressure systems, which provide a weak, but important forcing of the cloud field.

Another aspect, which may have been relevant this past week, is how the model uses observations to initialise the forecasts – data assimilation. By far the best source of information on cloud cover is satellite imagery, but when (as has happened this week) low cloud is accompanied by high “cirrus” cloud, the satellite only sees the high cloud, making the full extent of the low cloud difficult to determine, particularly over the oceans. Only when the high cloud clears, or the low cloud reaches land, can the extent of any forecast differences be established and corrected within the model.

We continue to work on improving both the computer model, and methods used to initialise the forecasts from observations. As shown below, a current test model (right) including changes to both the parametrizations and data assimilation produced a much better cloud forecast than the operational model (left) when compared to the actual cloud coverage shown by visible satellite imagery. Improvements like these should filter through to forecasts in the near future.

Visible satellite image at 11am on Thursday 6 April 2017 (above), with cloud forecasts from Wednesday evening valid for the same time, using the current operational model (below left) and trial version for future implementation (below right). Clear skies are represented by white with coloured shading representing clouds.

Despite these complications, our forecasts still offer good guidance: we’re consistently ranked as one of the top operational providers in the world for accuracy and we’re trusted by 84% of the public to provide weather and climate services.

As always keep up to date with the weather in your area using our forecast pages, Twitter or Facebook, as well as using our new mobile app which is available for iPhone from the App store and for Android from the Google Play store. Search for “Met Office” in store.

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One of the mildest March’s for the South East

Provisional full-month statistics show that East Anglia and South East & Central Southern England have had their equal mildest March since records began in 1910, and for the UK as a whole it was provisionally the 5th equal warmest March for the same period.

East Anglia had a mean temperature of 9.1°C, equal to 1938, while South East & Central Southern England recorded 9.2°C, equal to 1957. The UK as a whole recorded 7.3°C as its mean temperature for March 2017, equal with 1948 and cooler only than 1938, 1957, 1961, and 2012.


The highest temperature recorded in March was 22.1 °C at Gravesend, in Kent, on Thursday 30 March.  Tim Legg, climate scientist in the Met Office’s National Climate Information Centre, said: “It is very rare to go above 22 °C in March, with only three years since 1968 recording 22 °C or above, these are: 17 March 1990, when 22.6 °C was recorded at High Beach; and 23.6 °C at Aboyne in 2012.

“After this we have to go way back to 29 March 1968, when we recorded 25.6 °C at Mepal in Cambridgeshire: currently the all-time March record.”

As well as mild daytime temperatures March also brought mild nights to some.  England had fewer air frosts than in any other March since records of air frost began in 1961, with several stations in the south including Farnborough, Larkhill and Boscombe Down having had no air frosts at all this month.

The provisional rainfall map for March shows that the majority of the UK had around average rainfall, although Wales and north-west England were rather wetter. However, parts of South-Eastern England and northern and western Scotland received less rainfall than average , and for the UK as a whole it has been the driest Oct-Mar period since 1995/96.

Essex recorded the lowest total rainfall of any county in the UK, with just 26.3mm of rain falling, while Sussex received just 59% of its expected rainfall for the month (1981–2010 average).

As well as Scotland having just below the average rainfall for the month, it has also been the sixth sunniest March since 1929 with 123.8 hours of sunshine.

Provisional March 2017 data Mean temp (°C) Sunshine (hours) Rainfall (mm)
Actual  Diff from avg (°C) Actual % of avg Actual % of avg
UK 7.3 1.8 122.7 121   99.1 104
England 8.4 2.2 125.7 117   70.4 110
Wales 7.5 1.7 101.6 100 164.7 141
Scotland 5.4 1.3 123.8 133 127.9   91
N Ireland 7.2 1.4 120.6 123 106.3 112

No named storms occurred during the month. However, as Tim Legg added: “The UK was fortunate not to be hit by a storm, which brought some exceptionally strong and damaging winds to northern France on 6 March.”

As always keep up to date with the weather in your area using our forecast pages, Twitter or Facebook, as well as using our new mobile app which is available for iPhone from the App store and for Android from the Google Play store. Search for “Met Office” in store.

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March 2017: rather warm and dry for some

Provisional climate statistics up to the 29 March reveal that March 2017 has been a relatively warm month and has been rather dry in South-East England.

Despite a colder interlude in the third week of the month – which brought some frosts and snowfall in northern areas – the mean temperatures during March were above average for all parts of the UK. Indeed, the average temperature for March 2017 in south-east England is currently running as the second warmest March in a series stretching back to 1910. Across the UK it is currently running as the ninth warmest.

Underlining the month’s generally warm feel, a number of long-running English weather stations – from Cornwall to Yorkshire – recorded their highest daily minimum March temperatures. Additionally, long-running climate sites in Hampshire and Wiltshire (Farnborough, Larkhill, Boscombe) have for the first time in their records had a March without any air frost days.

Emphasising the warmth in south-east England, Middlesex was the historic county recording both the highest maximum average temperature and the highest average mean temperature: 13.6 °C and 9.8 °C, respectively. Middlesex was also one of a number of counties, including Essex, Hertfordshire and Surrey, which recorded the highest average March temperatures relative to their county’s respective long-term average (2.3 °C above the 1981–2010 climate average for March).

The highest temperature recorded so far this month is 22.1 °C at Gravesend, in Kent, on Thursday 30 March. Tim Legg – a climate scientist in the Met Office’s National Climate Information Centre – said: “It is very rare to go above 22 °C in March, with only three years since 1968 recording 22 °C or above, these are: 17 March 1990, when 22.6 °C was recorded at High Beach; and 23.6 °C at Aboyne in 2012.

“After this we have to go way back to 29 March 1968, when we recorded 25.6 °C at Mepal in Cambridgeshire: currently the all-time March record.”

Examining the provisional rainfall map for March (updated to March 29), it is clear that the majority of the UK enjoyed average rainfall. However, parts of South-Eastern England and northern and western Scotland received much lower rainfall than average.

Essex recorded the lowest total rainfall of any county in the UK, with just 26.2mm of rain falling up to the 29 March. Sussex was the UK historic county receiving the least rainfall compared with the long-term 1981–2010 average, with just 59% of the average March rain total.

With parts of north-west Scotland drier than average, the relative lack of rain-bearing cloud correspondingly boosted sunshine figures, with the region recording 121.2 hours of sunshine. This is a 40 per cent increase on what is normally expected in March.

No named storms occurred during the month. However, as Tim Legg added: “The UK was fortunate not to be hit by a storm, which brought some exceptionally strong and damaging winds to northern France on 6 March.”

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