Windrush Weather

Category: Commentary

  • Damp start but little total precipitation.

    Damp start but little total precipitation.

    The cool northwesterly breeze and variable sunshine on Sunday afternoon limited the rise in temperature to a maximum of 21.4C at 12.29 being 1.3C below average. The afternoon was marked by a rash of showers developing to the north of our area with the occasional one producing brief light rain and drizzle over our area at 13.00 and later at 13.35. The past night was again mild with a low of 12.2C at 06.57 due to the thick cloud cover. A longer shower of very light rain and drizzle arrived just before 07.30 that the precipitation in total for the twenty-four hours amounted to 3.6mm.

    The start to Monday was overcast with the drizzly rain that stopped just after 08.00. Both major forecasters gave a 90% confidence forecast of four hours of significant rain after 02.00 early on Monday over our area, however, they were both wrong as the heavy rain once again was to the east. At least the minimal precipitation has refreshed the plant life but only dampened the surface, which will soon evaporate.

    Today will be the last of the cool days with the breeze coming from the north. By Tuesday temperatures will begin to climb with some certainty that another heatwave will arrive later this week that could last much longer than the two heatwaves in June. The Jet Stream track by tomorrow will be to the north of the UK allowing a feed of hot air to arrive from the south that will build as the week progresses. This is due to the Azores High beginning to build a ridge of high pressure over the UK on Tuesday that could last into next week.

  • Cooler, cloudy day for Sunday, a time to recover before very it very likely heats up again!

    Cooler, cloudy day for Sunday, a time to recover before very it very likely heats up again!

    The thick cloud on Saturday produced occasional light drizzle in the morning and just after 13.00 with a more sustained fall of light rain and drizzle starting at 15.00 that in total amounted to 2.6mm. This precipitation refreshed the plants but so little it did not sink far into the ground. In fact, just after 15.30 the sun came out as the back edge of the cloud eased away eastwards, that saw the late sunshine lift the temperature to a maximum of 21.9C at 17.27 being 0.8C below average, the first below average this month. The UV level of 3.9 placed it at the top end of the ‘Moderate’ level, the lowest for a month.

    The cloud cover overnight meant a mild night with a low of 14.9C logged at 03.47 early Sunday.

    The new day on Sunday revealed total cloud cover, which is due to a cold front passing over the UK, which will be closely followed by another around midday, so little expectation of much, if any, sunshine today. The barometric pressure has dropped to its lowest for a month with a reading of 1007.4mb at 08.00, down a significant 22mb since Friday.

    The Azores High has now fully retreated to mid-Atlantic with the result our weather is influenced by the low pressure system to the north and northeast, in fact there are three of them, but none have a deep centre pressure. The realignment of the pressure systems will see the breeze come from the northwest today thus a cooler day combined with the cloud cover, and this wind direction will likely continue until Wednesday.

    The Jet Stream forecast sees it begin to loop north of the UK on Tuesday that will result in the hot dry weather becoming increasingly prevalent from Wednesday.

  • The weather today will be such a contrast to recent days.

    The weather today will be such a contrast to recent days.

    Although the peak solar activity on Friday was the lowest this month, peaking at 909W/m2, the strong, almost continuous sunshine pushed the temperature to a peak of 25.9C at 14.37 being 3.2C above my long-term average. The air was very dry after so many dry and hot days, I recorded a minimum humidity of just 33.9% at 15.17 before light, variable cloud arrived limiting the sun’s strength. At 14.00, when the thermometer read 24.8C, the heat index meant it felt more like 28.3C outside, taking into account the air temperature, wind strength and direction, humidity and solar strength.

    Looking at the back track of cloud and rain radar in the early hours of Saturday, there was evidence of a small cloud that brought very light and brief precipitation around 04.30, which was not measurable, hence recorded as a ‘trace’. There was just a little residual moisture seen first thing on Saturday on non-porous and previously very dry surfaces. The cloud cover gave us a mild night that saw the thermometer not sink below 14.6C at 05.20 being 2.7C above average.

    The start to Saturday revealed total cloud cover and a brisk wind from the west-southwest. The cloud and rain radar indicates that by mid-morning a cluster of clouds might pass our way, preceded by light drizzle, and might bring brief precipitation, but not persistent steady rain over a considerable period to quench the dry gardens. These very different weather conditions are thanks to the depression to the north edging down across the country producing a weather front that will have left the south coast later today.

    The weekend will bring us much cooler and cloudier conditions. However, by Tuesday the Jet Stream track is forecast to once again loop north of the UK that will see the Azores High begin to build and ridge back over the UK, which will mean the following days are likely to become very hot again.

  • One more fine day this week before a change on Saturday

    One more fine day this week before a change on Saturday

    Thursday gave us another fine, warm day that saw the thermometer eventually climb to a peak of 24.2C at 15.49 being 1.5C above average. However, thin cloud had drifted across by that time that limited any further rise. For the second successive night the minimum of 8.8C was below average at -3.0C, logged at 05.15, just after sunrise in Marlborough at 04.56.

    After a bright start to Friday variable cloud arrived around 07.30 that limited the strength of the sunshine. The warm, dry weather today is the result of a ridge of high pressure from the Azores High.

    This will be the last day of high temperatures this week as the recent anticyclone is splitting, as last week, returning from whence it came, with high pressure also building over the Continent. This relocation will allow a low-pressure system near Iceland to encroach over the UK bringing cloud on Saturday with little sunshine. In fact there is the possibility of some light rain, quantities probably limited, sadly, as any precipitation would be very welcome to gardeners for their parched gardens.

    High pressure has retreated to the southwest, back to the Azores, and this semi-permanent high pressure that we get near the Azores, known as the Azores High, has been ebbing and flowing from the southwest during the past week, hence this repeating cycle.

    The Azores High is a semi-permanent area of high pressure located over the eastern Atlantic Ocean typically near the Azores archipelago. It influences weather patterns across Europe as well as North Africa, and parts of North America.

  • Fine and dry with fresher air today after chilly night

    Fine and dry with fresher air today after chilly night

    The start to Wednesday did not follow the normal pattern as the lowest temperature is usually set during the early hours. The cold front that passed over the UK brought cloudy conditions along with cooler air that meant the minimum of 14.5C was logged at 09.21 although my records, with data read very morning at 08.00, indicated that the minimum overnight of 16.1C was set at 07.02.

    After 09.21 the cloud began to thin mid-morning with sunshine beginning to break through just before 11.00 and then building in strength that resulted in a maximum of 23.7C logged at 16.32. This high was exactly 1.0C above my long-term average but 6C below the high set on Tuesday. It was another dry day with the UV peaking in the ‘Very High’ category.

    The past night was very much cooler than recent nights with a minimum of 6.3C logged at 04.54, just before the sunrise in Marlborough at 04.56. This low was 5.6C below average and the coolest night since 23rd May.

    Thursday dawned with sunshine that slowly lifted the temperature to reach 16.9C by 08.00. The barometric pressure has risen a significant 12mb over the past twenty-four hours as an anticyclone begins to influence our weather for two days.

    The Azores high has been ridging across the country and also building that will bring us two days of fine, warm and dry weather. By Saturday this anticyclone will have separated into two components, one to the east and the other returning back to the Atlantic that will allow a low-pressure system, now just south of Iceland, to influence our weather with cooler, cloudy conditions.

    June 2025 Review

    Following the warm end to May it was quite a contrast to find that the beginning of meteorological summer began with numerous below average maxima. The days and nights were cool with very small amounts of daily precipitation after the previous three relatively dry and warm months. The heaviest fall was recorded on the 7th with 7.9m, which was deposited over many hours during the daytime and a light shower overnight.

    The brisk westerly breeze on the 7th and 8th originated from just south of Greenland, hence the moderated temperatures with a maximum of only 15.9C being 4.7C below my long-term average.

    A short drier period followed that saw temperatures increasing daily, especially by the13th as a flow of very warm air from Iberia had arrived that lifted the temperature to a maximum of 26.2C, being 5.6C above average.

    Often in winter I mention that wind chill is a factor as if outside it would feel colder than that indicated on a thermometer, referred to as the THW Index, that uses temperature, humidity and wind strength data. On the 13th the opposite was true when the THSW Index indicated if felt more like 30.2C outside on the skin, rather than the thermometer temperature of 26.2C, when the additional factor of strong sunshine was considered.

    High pressure saw the heat build from the 16th to the 21st with maxima well above my long-term average. The peak of 30.7C was logged on the 19th being a significant 10.1C above average. These conditions were brought about by hot, dry air drafted across on a southeasterly breeze from the Continent. The humidity level dropped very low in the afternoons to just over 40% on several days with the land drying out. There were several days when the equivalent loss of rainfall, through evaporation from ground sources and plant life, was in excess of 5mm daily.

    The heatwave threshold for the Marlborough area is 27C. A heatwave 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.

    There was a significant contrast in peak solar activity mid-month during several days when the wind veered into the west following days after a southeasterly was in control. The peak solar activity was at least 30% higher when the cooler, clearer air came from the Atlantic rather than the polluted hot air that had travelled across from the Continent brought on a southeasterly breeze.

    It was all change from the 22nd when low pressure to the northwest began to bring an Atlantic influence to our weather with maxima dropping closer to normal. The air having travelled over the sea was much less polluted than that from the Continent during the previous week. The peak solar radiation reached 1172W/m2 on the 24th compared to around 800W/m2 when we endured the hot, dry Continental air.

    The month finished with a heatwave, thanks to the Azores high pressure system, that once again saw three consecutive days when the maxima were equal to or above 27C to qualify as a heatwave. The peak solar activity occurred on the 29th when 1257W/m2 was logged at 12.52 just as the highest UV of 8.5 was recorded, which was at the top end of ‘Very High’. The last day of the month brought intense heat as the thermometer soared to a maximum of 31.3C making it the hottest day since 14th August 2022 when 33.2C was recorded.

    June 2025 was the hottest June I have recorded since the station was set up in 1984 with the average temperature a significant 2.5C above my 41-year average. It was not surprising to find that both the average maximum and average minimum were well above average at +2.72C and + 2.34C respectively.

    The total rainfall for June was 37.1mm being 70% of my 41-year average or minus 15.8mm. Due to the intense heat and warm winds the loss of equivalent rainfall due to evaporation from the ground and plant sources amounted to 116.1mm for the month.

    Although both January and February were wet months, because the following four months were much drier than average, the rainfall for the January to June period was only 296.2mm set against my 41-year record for that period of 390.9mm.