Author: Eric Gilbert

Monday 18th May
The first signs of a change in our weather were shown in the slightly warmer temperatures on Sunday with a maximum of 15.6C at 13.31 before cloud built up again, however it was still 1.7C below average but it was the warmest day since the 9th. Likewise, the overnight minimum of 7.2C, logged at 05.22 just after sunrise in Marlborough at 05.12 Monday morning, was higher. In fact it was 0.2C above average that made it the warmest night since the 10th.

The other quite clear evidence that the cold weather is on the way out is the temperature of the soil at a depth of 5cm, logged at 08.00, with 8.9C, 11.0C, 11.3C and 12.4C respectively for the last four mornings.

There was broken sunshine through gaps in the cloud first thing on Monday with the breeze now coming from a significantly different and warmer direction, the southwest. The low pressure to the west is now beginning to feed a warmer and more moist air stream across the country. By tomorrow there will be more of a southerly aspect to the breeze with likely significant rain in the early hours and a stronger breeze. The forecast surface charts indicate that by Thursday the low will give way to a high pressure over the Continent that will waft very much warmer air from Iberia with maximum temperatures getting well above average.

I will continue the series of images from Bowood House and Gardens in Wiltshire, which is only open for nine weeks during the flowering season. It is open this year until 7th June.

I recently came across this article from the Met Office that I thought might be of interest, part 2 tomorrow.

How the refreshed Met Office app is taking shape
Author: Met Office
Tue, 12 May 2026

You may have noticed our weather app has changed a lot this year, with a new design and various updates since it went live in January. So, what has been the process behind the refreshed app, what has changed since launch, and what’s coming next?

Here, we explain how we approach major digital updates, why listening to users is central to the process, and how this shapes the Met Office app as it evolves.

Moving on from legacy software
Since its launch in 2016, the previous version of the Met Office app kept millions of people safe and informed about the weather, from preparing for storms to planning day-to-day activities.

However, the technology behind the app had become increasingly difficult and costly to maintain, and feedback frequently highlighted a dated design.

The legacy infrastructure limited how quickly changes could be made and made it harder to deliver improvements users had been asking for. For example, the previous setup effectively required separate development for iOS and Android, meaning updates were slower, more complex and less flexible.

Refreshing the app allowed us to move away from those constraints. By rebuilding on modern technology, we’ve created a platform that enables faster updates, clearer design, improved accessibility and the ability to respond more quickly to feedback – while continuing to deliver the same trusted weather information.

Sunday 17th May
The bright and sunny start to Saturday was soon obscured by advancing cloud from a weather front heading in from the west. The increasing cloud meant the temperature by day was still depressed with a maximum of only 13.7C, being 3.6C below average, whilst the UV level of 3.8, a Moderate level, was limited. The rain radar indicated the rain area thinning as it approached southern England and breaking up, which was the reason the precipitation was just 0.2mm in a very light and brief shower at 15.40. The first signs in a turnaround in temperatures was observed last night with a minimum of 6.7C at 05.26, just after sunrise in Marlborough at 05.13. This low was just 0.3C below average and made it the warmest night since the 10th.

The reason for the first signs of a less cold weekend was due to the significant change in wind direction coming mainly from the west rather than the very cool air previously on a northwesterly breeze.

Sunday arrived with variable cloud and thus variable sunshine that had lifted the temperature to 9.8C at 08.00, the warmest start to a new day at that time since the 10th.

Changes in warmth will continue as the wind backs a little further to come from the southwest for the next two days, before coming from a significant southerly direction by Tuesday. The nights will be less cold, in fact perhaps close to or above average. It will take until Tuesday before the daytime temperatures reach average for May and then continue to rise daily as we approach next weekend.

The forecast charts indicate that Tuesday will be a very windy, wet day as a depression closes in from the Atlantic bringing the warmer air, however, ahead of it will be two weather fronts likely to produce significant rainfall. The total rainfall for May is just 10.8mm compared to my 42-year average of 59.5mm. By contrast, we have lost 45mm of equivalent rainfall this month due to evaporation from ground sources and plant life.

Saturday 16th May
It wasn’t until late in the day on Friday that the wind, at last, began to back from the persistent, cold northwesterly to come from a more wester.y direction. There was limited sunshine that once again, under the pool of cold air, meant another chilly day with the thermometer struggling to rise to a maximum of 13.2C, exactly the same as on Thursday.The overnight minimum was also similar to the previous night with a low of 3.3C at 03.12 early Saturday. The high was a significant 4.1C below average and the low was a significant 3.7C below average. In fact, we have now endured six consecutive days and nights with temperatures well below average.

Saturday arrived with broken cloud and brief glimpses of sunshine. The day ahead will see cloud build from mid-morning as two weather fronts cross the country with possible rain from the second cold front later in the afternoon, quantities uncertain. The rain radar at 08.30 showed shower clouds crossing Cornwall and Devon and heading eastwards.

The wind will continue mainly from a westerly quadrant for the next few days, which at this time of year is not a particularly warm direction, as the air circulates around the low to the north, still contains a pool of cool air. We will have to wait until Tuesday for warmer weather to arrive when the wind is forecast to back further and come from the south.

Friday 15th May
Once again on Thursday the flow of Arctic air, on a strong northwesterly breeze, depressed temperatures by day and night. The thermometer struggled to reach a maximum 13.2C at 17.13, in very welcome and warm late afternoon sunshine. This high was 4.1C below my May average. There were a few spots of rain on a couple of occasions only amounting to 0.2mm. During the late afternoon a couple of parallel lines of showers moved from north to south, just a couple of miles to the west and east, leaving Marlborough in the dry middle section.

The pool of cool air under thin cloud cover meant another very chilly night that saw the thermometer drop to a minimum of 3.6C at 03.08 early Friday.

The recent cool days and nights have seen the temperature of the ground fall away, due to the combination of strong winds of Arctic air from the northwest, resulting in the ground temperature at a depth of 5cm read at 08.00, drop from 14.4C on the 2nd to 10.3C, 9.1C and 8.9C respectively over the last three days. No wonder plants out in the garden are not thriving, especially with the lack of substantial rain. What precipitation has occurred over recent days has quickly evaporated.

Friday began with thin, high cloud and some brightness but no strong sunshine after dawn. We are still under the influence of the depression centred over Scandinavia, that will continue to feed Arctic air down across the country on a northwesterly breeze today, but less strong than of late. There is another trough of low pressure, within the large area of low pressure, forecast to cross the country as the day progresses, which is likely to see cloud thickening and possible precipitation this afternoon, quantities uncertain.

The barometric pressure is slowly rising with a ridge of higher pressure edging in from the west today that heralds a distinct change in our recent cold weather. By Saturday, the Azores anticyclone will have overcome the recent depressions to the east, cutting off the flow of cold Arctic Air, which will see an Atlantic pattern of weather return with a more moist but especially important, warmer air stream. From Sunday the nights will be less cold, due to the warmer flow of air on a westerly breeze, but we are likely to have to wait util Tuesday until maximum temperatures return to around the average and then above average by the end of the week when it could became pleasantly warm.

With the arrival of warmer air, more Spring like, I thought it appropriate for the next week or so to attach images from Bowood House and Gardens in Wiltshire to enjoy the wonderful Spring displays. Over the coming days I will take a walk around these magnificent gardens, full of colour at this time of year.

Thursday 14th May,
Wednesday was notable for the brief, but heavy showers that began around midday and occurred at intervals during the afternoon, which were accompanied by strong gusty winds that peaked at 32mph. The total precipitation was just 3.6mm. Due to the minimal sunshine and very strong wind from the cool northwest, the maximum of 14.5C was 2.8C below my long-term May average. The wind died down in the evening resulting in a minimum of 4.8C just after midnight at 00.22, being 2.2C below average in the pool of cool air.

There was a cloudy start to Thursday, that is likely to continue all day, with showers dotted around southern England, likely to build late afternoon. Further troughs of low pressure, circling within the large depression over Scandinavia, will bring us more disturbed periods during the day, on a northwesterly flow.

Regrettably, the low-pressure system over Scandinavia will continue to dominate our weather up the weekend, pushing air around its western flank, originating from near the Arctic, down across the UK on a cool northwesterly wind. Temperatures by day and night are not likely to return to average values until Sunday into Monday when the current low pressure to the east moves away and a deep depression arrives from the west, that will then take charge. This will return our weather to a more moist, but crucially milder air stream from the Atlantic driven on by an airstream from a westerly quadrant.

I attach the second half of an article from the Met Office on why air frosts occur in late Spring.

Clear skies and rapid cooling
One of the most important ingredients for frost is a clear night sky. After sunset, the ground loses heat as it radiates energy back into the atmosphere and out to space. Cloud acts like a blanket, trapping some of this heat and slowing the cooling process.

On clear nights, heat escapes more efficiently, allowing the ground and objects close to the surface to cool quickly. Even during late spring, when days are noticeably warmer, clear skies overnight can still allow temperatures at ground level to fall below freezing.

Wind plays a key role in determining how cold it becomes overnight. Light winds allow colder, denser air to settle near the ground, forming a shallow layer of cold air where frost can develop. Stronger winds mix the air, drawing in slightly milder air from above and reducing the chance of frost forming at the surface.

This is why frost risk is often highlighted on calm nights, particularly beneath areas of high pressure, which typically bring lighter winds and clearer skies.

Ground cooling and grass frost
In May, ground frost is more common than air frost. At this stage of the year, the ground has not yet accumulated as much stored warmth as it does later in summer. This means that similar air temperatures can lead to colder ground conditions than they would in early autumn.

Different surfaces also cool at different rates. Short grass, soil and vegetation lose heat more quickly than materials such as concrete or roads, which retain warmth for longer. As a result, grass frost can occur even when nearby paved surfaces remain frost-free.