Updated Tuesday 7 April 2015
At this time of year, despite still feeling quite cool, the sun can be as strong as it is in September. The UK often experiences higher than normal UV levels in April and May as a result of ozone anomalies, where pockets of low ozone move across the UK. This means that there is a higher chance than normal of getting sunburnt in prolonged spells of sunshine.
The main factors affecting the strength of UV radiation reaching the Earth’s surface are:
- the time of year
- the latitude
- the amount of cloud, dust and pollution in the atmosphere
- the amount of ozone gas in the stratosphere
The first three of these four factors are well-represented in our model, and so for the vast majority of the year, the UV forecast gives excellent guidance. However, the amount of ozone is currently modelled on climatology, i.e. the average concentration for the time of year. The presence of ozone in the stratosphere is important because it absorbs much of the UV radiation before it reaches even the top of the highest clouds in the atmosphere.
Our forecast for UV for this week is indicating generally moderate levels, however there is a possibility that where it is sunny or where the cloud is thin, UV levels may, in fact, be higher than forecast. UV can also be stronger at higher altitudes, so be aware and prepared if hill walking or mountain climbing this week.
If you are in an area that is sunny, make sure you take steps to ensure that you and your loved ones enjoy the sunshine safely, particularly as your skin may not be acclimatised to sunshine after the long winter months.
You can check the current levels of UV on the DEFRA Monitoring pages.
For more information on UV and ozone, visit our learning pages:
Official blog of the Met Office news team 