Wednesday saw the thermometer soar to a peak of 25.6C at 16.08, thanks to the wall-to-wall sunshine, it was also the warmest April day since April 2018, that also brought ‘High’ UV from 11.48 to 14.14. The night just past was much milder as the warmth was being held in the ground that had built up over the last few days with a minimum of 5.7C logged at 05.18 early Thursday, just before the sun rose over Marlborough at 05.40.
Thursday revealed another glorious start to a new day with strong sunshine after dawn, by 08.00 the temperature had risen to 14.1C. This is likely to be the last of the days with many hours of strong sunshine as the anticyclone is fading away eastwards, down 3mb since yesterday, we are now beginning to come under the influence of a depression just off the coast of Spain that will probably later today and tomorrow begin to throw thin, variable cloud over the area. There is not a great prospect of much rain unless thunderstorms suddenly break out under the heat as the humidity is a little higher today. The soil temperature at a depth of 5cm read 14.9C at 08.00.
April 2025 review
The high-pressure system just to the northeast of the UK became the dominant feature for the first week in April bringing fine dry days with wall-to-wall sunshine on many days.
The temperatures, as a result, rose well above average with a peak of 21.8C on the 4th that made it the warmest day since last September. However, the brisk wind, gusting up to 30mph, produced a wind chill so outside it felt much cooler, especially out of the sun.
The downside to the clear skies were the cool nights as the minimum slowly began to fall away with 4.4C, 2.5C, -0.1C and -1.2C on the 8th respectively making the latter the coldest night since 16th March.
The anticyclone that had been so dominant for many days eventually gave up the fight with the depression to the southwest beginning to elbow in and produce a significant change in our weather form the 12th as barometric pressure began to drop significantly. The first rain after seventeen consecutive dry days occurred during the evening and night of the 14th/15th, but the amount was minimal with just 0.8mm.
The first below average maximum was logged on the 14th being the first below average since the 17th March at -0.6C. This was due to cloud being thrown up from the depression moving up from Britanny, producing the widest and densest cloud bands since early March.
A depression edged in from the Atlantic on the 22nd that brought very welcome rainfall during the night amounting to 8.6mm being the wettest day since 26th February. This was a great help to gardeners as it had time to be absorbed by the soil, which was very dry. The previous 52 days had brought us just 8.8mm, much of which was very light and had quickly evaporated.
A ridge of high pressure built on the 24th and then built further to form an extensive anticyclone from the 25th resulting in the temperatures rising by day but giving chilly nights under clear skies, also more dry days. The maximum of 25.6C on the 30th was a significant 14.1C above my long-term average also the warmest days since 28th August 2024. Looking back through the records I found that it was the warmest April day since 2018 when a peak of 26.5C was logged.
The total rainfall for April amounted to just 11.7mm being only 20% of my 41- year average or minus 45.9mm. Not only was there minimal rainfall there was an equivalent loss of rainfall, through evaporation from ground sources and plant life, of 82.5mm due to the very warm days, of which 24 were totally dry.
It was not surprising to find that the average temperature for April was 1.6C above my long-term average. Only three maxima were below average during the whole month which is why the average maximum temperature was 2.9C above the long-term average whereas the average minimum temperature was just 0.2C above average.
There have been headlines in the press recently about heatwaves or mini heatwaves. An official heatwave occurs if we experience three consecutive days when the maximum exceeds the heatwave threshold, that naturally varies across the country. The threshold for Wiltshire was recently revised upwards to 27C.
Early morning fog was observed on two days also five air frosts were logged.
