Friday was the penultimate warm day this month when the thermometer rose to a maximum of 23.6C at 15.19 being exactly 6.0C above my long-term average. There were many hours of strong sunshine that again lifted the UV level into the ‘Very High’ category with value of 7.6, the highest since August 18th 2024. This high level occurred between 12.10 and 12.08 only, as variable cloud meant the afternoon brought variable sunshine with lower UV light, if only to the ‘High’ category. Another mild night has just passed under the influence of the sub-tropical air stream that saw the thermometer fall no further than a minimum of 12.4C at 05.42, which was 5.4C above average. The low was some 45 minutes after the sun rose due to the formation of radiation fog, mainly in the valleys around Marlborough.
Saturday after dawn revealed that radiation fog had filled the valleys of the River Og and River Kennet in the early hours that at 06.30 limited visibility to 400m whilst over the Marlborough Downs and Savernake Forest the fog was far less dense and to the east visibility was not far from normal, just misty conditions. The wind will continue from a westerly quadrant and be light in strength. The strength of the sun was very strong that by 07.00 almost all evidence of the fog and mist had cleared and visibility was ‘good’.
Today will be the last of the very warm days that have been thanks to a stream of sub-tropical air from near the Azores. During this evening a cold front, associated with the depression just to the northwest of Scotland, will pass over the UK bringing much cooler air. The week ahead will bring more unsettled weather but at the moment little evidence of any substantial rainfall.
The May rainfall total was just 23.9mm being only 40% of my 41-year average, being the driest since 2020 when just 8.2mm of precipitation was recorded.