Author: Eric Gilbert

After intermittent brief rain showers and light drizzle during Sunday morning the sky cleared early afternoon with bright sunshine lifting the temperature to a maximum of 21.9C at 16.02, however, this was 0.8C below average. The additional precipitation of 4.4mm took the monthly rainfall total to 20.7mm compared to my 41-year average of 59.8mm. Every little helps but it was insufficient to take moisture to any useful depth in the gardens. I was surprised to see how low the temperature dropped overnight when a low of 8.7C was logged at 05.02 early Monday.

Monday revealed a very different scene to recent days. The low temperature in the early hours, combined with the recent moist air, caused fog to form in the early hours, as the moisture condensed, limiting visibility to 200m. By 07.00 there was a distinct improvement in visibility and at 07.50 brightness was observed as the sun got to work that had lifted the temperature to 13.3C by 08.00. The recent high pressure is now well to the east over Africa and Russia that will result in the resident low-pressure systems bringing us average maxima with variable cloud and possible occasional showers.

For the next three or four days we will have unsettled weather that is entirely due to low-pressure systems now dominating our weather. Currently there are three modest depressions, none deep, surrounding the UK, one over Scotland, the second over East Anglia and the third in the eastern Atlantic. The wind today will begin by coming front the north-northwest that by early afternoon will have backed into the west as these weather systems slowly relocate. There are signs that by Thursday an Azores high pressure will try and edge in from the west, settling down the weather to drier, sunnier conditions with maxima returning above average, but no heatwave.

The butterfly is a Meadow Brown.

The unsettled weather was very much the pattern for the weather on Saturday they gave us a cloudy and damp morning, with brief, light rain at 11.50, before it brightened up late morning with a slow increase in temperature resulting in a maximum of 24.9C at 15.07 being 2.2C above average. The forecast rain arrived in the early hours with the automatic rain gauge triggered at 03.15 with modest, intermittent rain until 05.30 that amounted to 4.2mm. The additional precipitation took the monthly total to 16.4mm against the 41-year average of 59.8mm. The thick cloud cover overnight meant another mild night with a minimum of 15.9C logged at 04.03 being exactly 4C above average.

The arrival of Sunday revealed the low cloud cover with slight, brief drizzle observed starting again just before 08.00. The rest of the day will bring limited sunshine with occasional showers.

The overnight rain radar showed a 10 mile wide band of heavy rain moving northwards between Marlborough and Hungerford with a narrower band to the west with a short period of heavy rain over Devizes. The rain in the early hours was useful in partly refilling two of my water buts but carefully removing the top layer of the soil revealed that the rain had only reached a depth of less than 2cm of top soil, which will quickly evaporate in any sunshine later today. At least I have a limited supply of rain water to use in my watering cans when the hosepipe band starts on Tuesday!

The reason for the unsettled weather can be laid at the door of two small depressions close to the UK, today one is over Brittany and the other just off the coast of west Wales that are producing the thick, low cloud and bands of rain. The barometric pressure reading at 08.00 was 998.8mm, the lowest pressure since 15th April.

The picture is of a Cydalima perspectalis or the box tree moth, first described by Francis Walker, the English entomologist, in 1859. Native to Japan, China, Taiwan, Korea and India it invaded Europe being first recorded in Germany in 2006 , then Switzerland and Netherlands in 2007 and Great Britain in 2008.

Under the strong sunshine on Friday, muted late morning and in the afternoon due to thin, high cloud, the temperature rose to its highest at 16.49 with a maximum of 26.2C being 3.9C above average also the warmest day since the 13th. The peak UV of 7.1, which is in the ‘Very High’ category, occurred at 12.37 for just four minutes, during a strong blast of sunshine, an hour before and two hours after that time, was rated as ‘High’. The other significant feature on Friday was the minimal air movement, just a gentle breeze, between calm periods, with the strongest movement on one occasion of just 9mph, couldn’t be called a gust.

Saturday arrived with thick, low cloud and the first rain drops observed at 06.15, that began a short, very light shower until 07.15, that amounted to only 0.7mm. The humidity that was high yesterday, due to the moist, southwesterly air flow, had risen to 91.4% at 08.00 thanks to the disturbed area that arrived overnight. The breeze will be ight again today backing a few degrees from west-northwest in the morning to southwest later today.

The intense, wide rain area that drifted across from the Continent overnight, once again travelled to the east of our region. There were also narrow bands to the west over East Devon, Dorset and Somerset, but a wide dry area in between. Once again I wonder if there is a geographical reason for the repeated pattern of storms arriving from France dividing to the west and east of Central England. It is very frustrating for local gardeners when we are about to come under a hosepipe ban on Tuesday!

This month has brought us the grand total of 12.2mm compared to my 41-year average of 59.8mm.

The image is of a Red Admiral warming itself on a convenient stone.

Thursday gave us a very cloudy morning and early afternoon that limited the rise in temperature to a maximum at 13.38 of 25.9C, being 3.2C above average. That broke the recent pattern of heat building throughout the afternoon. The reason was a very moist air stream from a warm weather front that crossed during the day. This weather pattern gave us another very mild night with a low of 16.0C at 03.41, which was 4.1C above average. The humidity at 16.00 was high at 64% and by 18.00 had risen to 78% when last week I was registering humidity around 40% in the afternoons.

The start to Friday was in contrast to recent mornings as the very moist air and low cloud meant the Marlborough Downs and Savernake Forest were draped in cloud. Initially, the visibility was limited to 500m, but this improved very quickly that by 07.50 had lifted into low cloud. The humidity at 08.00 was 89.1%, the second highest this month. The cloudier conditions today are thanks to a cold front crossing the UK. There are currently three modest low pressure systems around the UK so unsettled conditions are likely for the next few days, with sunshine and possible showers also less extreme temperatures.

The recent heatwaves made headline news with three in succession have occurred in 2025, so far, when the heat threshold for Wiltshire of 27C was equalled or exceeded. I have analysed the last thirty years of my records to find the incidence when a daily maximum of 27C was equalled or exceeded and discovered a distinct rising trend over that period. In the early 1990’s there was an average of 7 days when those conditions were met whereas in the 2020s that figure had risen significantly to 14 each year, on average. The extremes were in 1998 when no days reached a maximum of 27C, which contrasts with the year of 2018 when 28 days of 27C or above were recorded. This year we have so far had 13 days when the maximum of 27C or above was recorded.

The image is of a scarlet tiger moth, active during day and night. It flashes its red hindwings as a warning to predators.

The temperature recovered on Wednesday with a maximum of 25.4C early in the afternoon being 2.7C above average. This early afternoon peak was the result of thin cloud beginning to edge in from the west after around midday and then thickening, hence no further rise as the afternoon progressed as occurred during previous, hot days. Once again, overnight cloud cover meant a mild night, an exceptionally mild night, with a low of 17.6C at 05.46 being 5.7C above average. The low was only 5C below the average maximum for July.

Thursday revealed a cloudy start to the new day with misty conditions before 06.00 over the Marlborough Downs, albeit with some brightness in the east first thing. There was evidence on smooth surfaces of some precipitation, so I suspect light drizzle had fallen a little earlier. The cloud is thanks to a warm weather front slowly crossing the country today bringing not only warmth but moist air from the Atlantic. The humidity at 08.00 was 81.5%, the highest since the 7th when 91.9% was logged after the light rain on the previous day. The barometric pressure at 08.00 read 1017.5mb up just 1mb since Wednesday.

The high pressure will slowly east eastwards over Scandinavia and Russia as the day progresses with a low pressure system to the northwest trying to edge closer today and tomorrow, however, this will not have a major effect on what will be a hot, dry day on Friday, thanks to the residual high pressure. It will be Saturday and Sunday before we come under the influence of the depression as it then centres over the UK with lower temperatures and more cloud.

The total July rainfall to date is just 11.4mm being only 19% of my 41-year record. Set against the minimal rainfall is the equivalent loss of rainfall due to evaporation from ground sources and plant life that now totals 71mm. Although the daily total varies according to the weather there has been an average loss of over 4mm each day, the greatest loss was 6mm on the 12th under the blazing sun and very high temperatures. By contrast there was loss of just 2.3mm on the 15th under the more moist southwesterly breeze and lower maximum.

The butterfly is a Hedge Brown on Ragwort