Monday 11th August.
The temperature soared higher than expected on Sunday with a maximum of 27.4C, logged at 16.31 under strong sunshine. In fact the heatwave condition of 27.0C was reached at 16.14 with such a peak not expected until today, Monday. The high was a significant 5.3C above my long-term August average and the hottest day since 25th July (27.7C). Looking at the back track of temperature it was a steady increase all day with a slight increase of cloud around midday that tempered the rise for a couple of hours. Under a clear sky the thermometer dropped to a minimum of 9.7C at 05.31 early Monday, just before sunrise in Marlborough at 05.46. However this halt to the decline in temperature also coincided with variable, high cloud drifting in from the west just after 05.00.
The start to Monday revealed high, thin cloud that initially tempered the rise in temperature, however, bursts of strong sunshine before 08.00 meant the thermometer had risen to 17.7C by 08.00, the warmest start to a day at that time since 17th July (21.2C). More variable cloud arrived after 08.15.
The high pressure has relocated a little further east that will produce an air stream from the southeast, which will waft hot and humid air from the Continent. Over the next day or two the depression in the eastern Atlantic, just off the Bay of Biscay, will edge northwards. The result will be a combination of the air circulating clockwise around the anticyclone combining with the anticlockwise rotation of air around the depression, which will produce even higher maxima that will confirm an official Heatwave has occurred.
The heatwave threshold for the Marlborough area is 27C. The maximum yesterday was above that figure, which will happen again today and also tomorrow. Thus we are technically experiencing a heatwave, which is described as three consecutive days with temperatures rising above the heatwave threshold. The original heatwave thresholds were based on the reference climate period of 1981-2010 and were intended to be flexible and revised in the light of climate change, therefore the heatwave thresholds were revised in 2022, using the most recent 1991-2020 climate averaging period, with the local threshold temperature rising from 26C to 27C. The review saw six counties move from 27C to 28C, one from 26C to 27C and one from 25C to 26C, the areas changed were in the south of the UK and the Midlands.
The Savill Garden is Grade 1 listed on the Register of Historic Parks and Gardens.
Update:
26C at 11.25
27C at 12.15
28C at 13.37
29C at 14.29