The last few days have been unseasonably warm but why is this happening so early in the year? The answer lies largely in the air flow directly above the United Kingdom but more importantly where that air has come from.
Over the last week or so we have been under the influence of high pressure which has given us very settled conditions, with light winds and a lot of sunshine. During the daytime, the sun has injected plenty of warmth and the light south to south-easterly winds have drawn further warm air towards us from continental Europe.
We would normally expect average maximum temperatures in March to edge into double figures across the south of the country and stay much cooler further north. However, over the last few days temperatures have reached the low twenties and we have seen a new record high for Scotland in March as the temperature reached 22.8 °C at Fyvie Castle in Aberdeenshire on Sunday 25 March and temperatures are expected to reach similar values over the next couple of days.
The last time we had a comparable warm spell in March was during 2005 between the 16th and 26th when temperatures reached 21.8 °C at Kew Gardens on the 19th. Before that we have to go back to 1968 and 1965 when two shorter spells (which coincidentally both happened for the same two-day period in March, from 29th to 30th) saw highs of 25.6 °C at Mepal, Cambridgeshire and 25.0 °C in Wakefield respectively, both on the 29th.
The settled and clear conditions by day continue during the night time and allow much of the sun’s energy to escape from the earth’s surface back into the atmosphere, allowing temperatures to fall quickly after dusk. So, in contrast to the warm, sunny days, the nights are clear and cool, especially this time of year. Although we are seeing temperatures reaching in excess of 20 °C by day, we have seen overnight minima fall below freezing in some areas and many of us are waking up to frosty mornings. With light winds, mist or fog patches are also likely to form.
The weather forecast for the next few days remains settled and warm for much of the country with temperatures in the high teens or low twenties. But later in the week, the area of high pressure will drift to the west of the UK and allow a northerly wind to bring in more cloud and cooler air to all parts, with the chance of a few showers.