Annual Count of Summer Days (annual number of days where the maximum daily temperature is above 25°C), projections for a range of future warming levels from UKCP18. Provided on a 12km BNG grid.Summer days is a measure of the health impact from high temperatures and heatwaves - it is based on temperature thresholds which, when exceeded, can pose risks to human health and wellbeing. Summer Days are shown to increase everywhere throughout the UK. There is a higher frequency in the South of the UK, and this is projected to increase considerably with global warming. Tropical Nights is another metric measuring health impacts of high temperatures.This data contains a field for each warming level. They are named 'Summer Days', the warming level, and 'upper' 'median' or 'lower' as per the description below. E.g. 'Summer Days 2.5 median' is the median value for the 2.5°C projection. Decimal points are included in field aliases but not field names e.g. 'Summer Days 2.5 median' is 'SummerDays_25_median'. Data defaults to displaying 'Summer Days 2.0°C median' values, use 'change style' to display other values.The warming levels used are 1.5°C, 2.0°C, 2.5°C, 3.0°C, 4.0°C, and two baselines are also provided for 1981-2000 (corresponding to 0.51°C warming) and 2000-2017 (corresponding to 0.835°C warming).What is the data?The data is from the UKCP18 regional projections using the RCP8.5 scenario. Rather than giving projections for a specific date under different scenarios, one scenario is used and projections are given at the different warming levels. So this data shows the expected number of Summer Days should these warming levels be reached, at the time that the warming level is reached.For full details, see 'Future Changes to high impact weather in the UK'. HM Hanlon, D Bernie, G Carigi and JA Lowe. Climatic Change, 166, 50 (2021) https://doi.org/10.1007/s10584-021-03100-5What do the 'median', 'upper', and 'lower' values mean?This scenario is run as 12 separate ensemble members. To select which ensemble members to use, a single value was taken from each ensemble member - the mean of a 21yr period centred on the year the warming level was reached. They were then ranked in order from lowest to highest.The 'lower' fields are the second lowest ranked ensemble member.The 'higher' fields are the second highest ranked ensemble member.The 'median' fields are the median average of all ensemble members.This gives a median average value, and a spread of the ensemble members indicating the level of uncertainty in the projections.This dataset forms part of the Met Office’s Climate Data Portal service. This service is currently in Beta. We would like your help to further develop our service, please send us feedback via the site - https://climate-themetoffice.hub.arcgis.com/