Sunday 23rd August
After a sunny morning on Saturday a little variable, fair weather cloud did bubble up, but not as much as on Friday, which was why the maximum of 21.8C was logged late afternoon at 17.38 and just above the average (+0.2C) after the cool day on Thursday. The past night under a clear sky and the cool air stream from the northeast saw the thermometer drop away to a low of 6.3C at 06.04 being 5.4C below the late August mean.
Sunday began with strong sunshine that lifted the temperature to 12.6C by 08.00, which made it the coolest start to a new day this month. As the ridge of high pressure slowly relocates to the east the wind will veer from northeast to east as the day progresses, but be very light. The light breeze dropped out after 02.00 this morning. Today will probably see a similar pattern to the past two days as light cloud will probably bubble up during the afternoon. The barometric pressure today at 08.00 read 1026.2mb, the highest all month, and rising slowly.
The high pressure, ridging in from the southwest, will maintain the dry and fine weather on Sunday and probably until Wednesday with maxima returning to just above the August average. The low pressure off the coast of Iberia is forecast to edge towards the UK over the next few days. By Wednesday the forecast charts indicate five separate mini centres of low pressure to the west that by Thursday will have joined forces and bring us a cloudy and possibly very wet day that might contain thunderstorms. This realignment of weather systems will see the wind make a significant change in direction to come from the south, which will dictate our weather over Thursday and Friday bringing unsettled conditions.
From time to time over the past week or two I have seen headlines that suggest there could be another heatwave in September. I have seen nothing in the meteorological data that at this time indicates that temperatures might rise very high again. However, as a matter of interest I have analysed my statistics when the heatwave threshold of 27C for Wiltshire has been equalled or exceeded over the past fifteen years. Taking three five-year spans I found that from 2012-2015 there were 15 days, the period 2016-2020 the heatwave conditions totalled 57 days and from 2021-2025 there were 76 heatwave days. A distinct upward trend in the occurrence of heatwave days is obvious. The year with the highest number of heatwave days was 2028 with 25, followed by 2025 with 21. So, how many this year so far – 37!