A cooler, wetter outlook heading into July
After a warm and largely dry first half of June, the weather pattern is in the process of a large-scale change to a cooler, more unsettled one for the next few weeks. High pressure is expected to linger to the west and southwest and keep low pressure nearby or overhead. This will promote more unsettled and cooler weather to stick around into July, with temperature near or slightly below average. Toward mid-July the pattern is likely to be rather changeable with mixed dry and warm spells and a increasing chance of a brief heatwave.
Fresher Atlantic air brings some rain
A low pressure system will tend to keep things cloudy and rainy for much of the country, with some heavy or thundery showers in places. However, Scotland will tend to escape the bulk of the rain and have a drier, but dull weekend. We expect things to be changeable with a drier, sunnier start giving way to a cloudier, wetter end as more low pressure systems move in. Temperatures are likely to remain near or slightly below average throughout, although there's a small chance of some warmer air next weekend.
Staying unsettled with changeable temperatures
As we head into July the large-scale weather pattern is expected to change from what we experienced for the first part of June. High pressure is expected to build in the North Atlantic to the west of Europe while another high in Russia builds off to the east. Between these high pressure zones an area of low pressure is expected, which will often be nearby to the UK in Northwest Europe. This will lead to a more unsettled pattern for the UK with wetter and at times windier conditions and fewer dry and sunny days. At the same time, temperatures will trend a little cooler with northwestly or northerly winds bringing in some fresher Atlantic air from nearer to Iceland.
This type of weather pattern is notorious for the day-to-day variability that can be difficult to predict more than about a week ahead. We can say with high confidence that we expect the large-scale weather pattern to develop by early July but we only have medium confidence on the specific details, especially with the temperatures.
If high pressure builds more frequently and stronger than expected around Germany, then we could end up with southwest winds instead of northwest winds. This is still a wetter pattern for the UK but it's also much warmer with temperatures generally above average. There's a smaller chance high pressure could also build overhead and push lows into Scandinavia. This is both a drier and warmer pattern. However, neither of these patterns are especially hot, which would require winds from the south.
A cooler and unsettled pattern with dry spells
The first half of July is showing some compelling signals for the large-scale weather pattern across the Atlantic and Europe to remain mostly the same. That is, high pressure will often be to our west and southwest (and well off to the east) while low pressure is nearby or overhead. This will keep things more unsettled and cooler than normal for July with some very wet days likely at times.
The high in the Atlantic will occasionally send some more transient high pressure systems through northern Europe. These will tend to shift eastward and only stick around for a few days at a time, but they will bring some sunnier and drier weather to break up the unsettled spells. If any of these highs get trapped in Germany for too long, we will see warmer days mixed in as well. All this adds up to a rather changeable outlook for July, although we anticipate any warmer, sunnier days will be brief spells rather than the norm.
The extent of high pressure influence in western and northern Europe is the main source of uncertainty for the forecast. Computer models are very enthusiastic on developing a strong high to our east over Germany and into Scandinavia by mid-July. This would be a very warm pattern for the UK with a potential for heatwaves. However, the computer models have been very poor at long range pressure forecasts in recent months and it is likely they are a little too optimistic on the chances for hot weather. Instead, we expect the cooler pattern to become increasingly broken up with warm, dry spells as high pressure struggles to build into Europe. There is a 30% risk that high pressure builds in strongly and we see warmer weather with a greater risk of heatwaves.
Any signs of warmer weather to start the school summer holidays?