The thermometer rose steadily on Tuesday to reach a maximum of 28.6C. This was a significant 9.7C above the 39-year average and the hottest day since 25th June (28.7C). The threshold for a heatwave for Wiltshire is a minimum of 27C for three consecutive days, therefore, if the thermometer rises to a peak of 27C or above today, it can be classed as a heatwave. Three neighbouring counties to the east of Wiltshire had their threshold lifted to 28C last year due to the continuing rise in global temperatures. The UV value of 5.2 was still in the High category.
The low of 13.4C was identical to Monday night being 4C above the average. This was far from a ‘tropical night’ that needs a minimum of 20C to be so described.
Wednesday dawned with misty conditions that meant the sun was initially weak. However, by 08.00 the thermometer read 15.7C. The barometric pressure continues high with a reading of 1019.7mb at 08.00. The hot, moist airstream continues to be brought from the Continent on a very light wind varying between northeast and southeast as the result of high pressure over Scandinavia and low-pressure over the Atlantic, the former rotating clockwise and the latter anticlockwise, feeding the air from the Continent.
Update: a maximum of 30.3C was recorded at 15.54, making it the hottest day this year. This was also a September record for my station set up in 1984. The previous high was 27.1C in 2020. I confirm that we are experiencing a meteorological’heatwave’ as we have endured three successive days with a maximum in excess of 27.C
