Friday 14th August
Thursday gave us the most intense heat of the current heatwave that saw the thermometer soar to a maximum of 35.9C at 14.03. This high created a new August maximum record for my station, which was a significant 14.3C above average. Between 12.00 and 13.00 lumps of cloud temporarily limited the rise, also thinner, variable fair weather cloud during the afternoon meant the high was reached in the early afternoon rather than late afternoon.
The heat was very reluctant to drain away during the past night, which resulted in another very warm night with the thermometer only slowly falling away to a minimum of 16.3C at 06.25, some 35 minutes after the official sunrise time.
On greeting the new day on Friday I observed that radiation fog had formed in the River Og valley during the early hours, which had evaporated by 06.10. Looking at the back track of the cloud radar it showed that an isolated large bank of cloud had developed, stretching from near Salisbury to just south of Swindon, which produced the low cloud draping the Marlborough Downs that blocked the early morning sunshine. This gave us a very welcome cooler start to a new day and the later minimum temperature. It wasn’t until 07.30 that the sun began to break through and then not strongly until just before 08.00, by which time the thermometer read 19.1C. The humidity reading of 91.7% at 08.00 was the lowest this month due to the low cloud.
The high pressure over the past day has eased that has allowed a cold front to form to the north, which will traverse southwards across the country today passing over our area tonight, so another hot day ahead but less intense than recently. Sadly, the weather front will contain just cloud with no precipitation.
Behind the cold front the air will be cooler as a result of the change in wind direction. Yesterday the southerly air flow wafted more heat from the near Continent. The change has already begun, coming from the west-northwest today and probably from a more northerly direction on Saturday. This will result in maxima slowly falling day by day that by midweek should see peak temperatures much closer to the average for August, when we will likely come under an Atlantic weather pattern.
The rate of evaporation has been more consistent over the most week after the light rain on the 4th, averaging just under 5mm a day. To date the equivalent loss of rainfall due to evaporation from ground sources and plant life is 58mm that contrasts sharply to the rainfall of just 1.2mm.
What are heat domes? And are they getting worse?
Author: Met Office
Wed, 12 Aug 2026
As temperatures continue to reach exceptional levels across parts of the world, one term appears again and again in news reports: heat dome.
It is often used to describe some of the most intense and long-lasting heatwaves, particularly those that shatter long-standing temperature records.
But what exactly is a heat dome, how does it develop, and are these events becoming more severe in a warming climate?
What is a heat dome?
A heat dome develops when a large area of high pressure becomes established over a region and remains there for an extended period. Under high pressure, air sinks through the atmosphere. As it sinks, it becomes compressed and warms. At the same time, cloud formation is suppressed, allowing strong sunshine to reach the ground.
The longer this pattern persists, the greater the heating effect. Clear skies encourage daytime temperatures to rise, while soils gradually dry out. As ground moisture decreases, less solar energy is used for evaporation and more becomes available to directly heat the land surface and the air above it.
This creates a feedback loop where dry ground promotes additional warming, which in turn encourages further drying. Because warm air occupies a deeper layer of the atmosphere than cooler air, the resulting pattern can resemble a dome-shaped area of heat that becomes difficult to dislodge.
At the Met Office, the term “heat dome” is used less frequently, with meteorologists often referring instead to persistent summer blocking highs. However, the underlying meteorology is largely the same.