28-07-2025
Week-long summer holiday heatwave could leave parts of Wales baking in 35C
Ridges of high pressure over the Continent have the potential to bring extreme heat to Wales and England in the second week of August. A heatwave lasting a week or even longer is being forecast by one weather model with the mercury soaring to 37C in places.
GFS model runs suggest heating building on Sunday, August 3, and peaking on Sunday, August 10. If this happens, Monmouthshire could see highs of 35C with the North Wales coast hitting 31C.
Forecasts suggest the heat slowly ebbing from west Wales on Monday, August 11. However Border counties could still see highs of 31C-33C, with a scorching 37C in central England.
Hot weather from Spain and Portugal is currently being held at bay by low pressure trapped by the Jet Stream. An Azores high is nudging into southwest Britain, creating a north-south divide which is expected to remain the dominant pattern into early August – rain further north, more settled in the south.
But by the second week of August, the Azores high could break free of its shackles.
Writing over the weekend, Netweather meteorologist Ian Simpson said: 'Longer range outputs from the GFS model indicate that, from there, it won't take much to get some of that hot weather in Spain and Portugal spreading back northwards through western Europe, should one of those ridges of high pressure head eastwards into central Europe.
'This is a long way off, and substantial heat through Britain and France looks unlikely for at least another 10 days.'
Despite this, the Global Forest System (GFS) indicates heat starting to build next weekend, from Sunday, August 3, initially in southern Britain. By Tuesday, it forecasts the plume of warm air reaching east Wales, bringing highs of 24C in Monmouthshire and 23C further north.
During the course of the week, the warm air is modelled to slowly move into northwest Wales, peaking over the second weekend in August. On current forecasts, only northern Anglesey and the tip of the Llŷn Peninsula may miss out.
On Sunday, highs of 33C could be seen in mid and northeast Wales. Temperatures on the North Wales coast are set to be a balmy 31C, with Gwynedd's western coast hitting 28C-29C. Hot weather may persist over England into the following week, the GFS model suggests.
Forecasts at this range are mired in uncertainty and not all models agree. For example, ECM forecasts suggests any influx of heat over Britain could struggle to reach Wales and northern England.
However the Met Office said there are 'hints of a more settled August", with 'tentative signs of a more settled spell developing' early in the month.
Thereafter, the national forecaster remains cautious. 'Some models are hinting at a Scandinavian high building to the north of the UK, which could bring drier and warmer conditions,' it said.
'However, confidence remains low at this range.'
