Very cool night!

After the coolest day this month with a maximum of 22.8C, being 1.7C above the average, the thermometer dropped very low overnight under clear skies to a minimum of 5.8C. This low was 5.9C below the average and the coolest night since 6th July. The lower temperatures were due to the cooler air brought on the northwesterly breeze that was more brisk on Friday with a maximum gust of 18mph.

Saturday arrived with more sunshine after dawn that lifted the temperature to 13.4C at 08.00. The high pressure has been building over the past three days and at 08.00 read 1030.1mb, the highest since 9th July.

Review July 2022

Although the month began with temperatures average or just below it began to hot up from the 6th as pressure built up with an anticyclone in mid-Atlantic.

A technical heat wave occurred from the 10th to the 12th as temperatures were equal to or above 27C , the heat wave threshold for Wiltshire. A peak of 30.5C was recorded on the 11th.

During the first two weeks rain was recorded on just one day when 4.3mm fell.

Under an anticyclone over the UK from the 13th to 16th maxima were a couple of degrees above the average but followed by cool nights, 6.7C early morning of the 15th was 5.2C below the 38-year average.

A ‘Spanish Plume’ began to make itself felt on the 16th as the anticyclone eased eastwards to be replaced with a developing depression just to the west of Portugal. This meant a change in wind direction, from north then west so that the southerly air flow brought intense heat from North Africa, across Spain, Portugal then France, arriving with a vengeance on the 17th.

The Metrological Office announced an ‘Extreme Heat Warning’ from the 17th, this type of warning was only introduced in 2021. They forecast that the extreme heat would be ‘absolutely unprecedented’.

The extremely hot days of 18th and 19th will be remembered for a long time as the thermometer climbed to 35.8C and 36.7C respectively. Both these broke the previous record of 34.9C on July 19th 2006. It was technically a heatwave for Wiltshire as 27C or above was recorded from 16th to 19th.

Moderate showers on the 20th, amounting to 8.0mm, broke the dry spell of 17 continuously dry days. Two further but very brief showers occurred on the 25th and 31st that added just 1.0mm to the total.

The temperatures began to build again during the last week with a high of 26.6C.

The mean temperature for July was 1.3C above the 38-year average principally due to the hot days. The mean maximum was 2.47C above the average whereas the mean minimum was just below due to cool nights at the beginning of the month.

The minimal July rainfall of 14.1mm was 45.3mm below the 38-year average and the driest July since 1999 when just 10.1mm was recorded. By contrast July 2007 brought us a deluge with 127.2mm of rainfall. It has been the driest January to July rainfall since this station began in 1984 being 186mm below the average.

There has been a great variation in diurnal temperatures, the difference between day and night. On the 18th there was a range of 25.6C between the maximum of 35.8C and minimum of 10.9C. By contrast, the variation on the 25th was just 6.4C.