The Met Office has warned that the Vale of Glamorgan could see showers develop from Thursday evening into Friday, bringing a risk of thunder alongside the downpours.
Monday is expected to remain dry across Barry and Penarth, with less than a five per cent chance of rain throughout the evening. Some cloud may develop overnight, with the possibility of patchy fog forming in the early hours.
High temperatures are forecast for Tuesday, with the mercury expected to reach around 30°C in Cardiff and Barry.
The rain risk will stay low, remaining under five per cent for most of the day and rising only slightly to around 10 per cent in the evening.
Wednesday is predicted to be the hottest day of the week, with the Met Office warning of “extreme heat” reaching up to 33°C in Cardiff and potentially as high as 36–37°C in some areas near the coast.
Humidity levels are also expected to be high.
Rain remains unlikely, though there is a brief 10 per cent chance of showers around 7pm.
Thursday marks the most significant change in the forecast, with the potential for rain and thunderstorms from late evening onwards.
There is a 20 per cent chance of thunder showers around 10pm, increasing overnight.
The Met Office has indicated that “a few heavy, perhaps thundery showers” could develop during the day, though sunshine and temperatures between 28–33°C are still expected.
Some misty low cloud may be present in parts of the region during the morning.
Friday and the weekend are forecast to be less hot but still largely settled and dry.
High pressure is expected to keep most areas rain-free, though isolated thundery showers are still possible.
The Met Office’s outlook describes conditions from Friday to Sunday as “dry and settled” with “plenty of sunshine.”
Any low cloud or fog that forms overnight is expected to clear quickly each morning.
For those planning outdoor activities or heading to the coast, the most reliable dry weather is expected from Monday through to Wednesday daytime.
The main risk of rain—and the potential for thunder—arrives on Thursday evening.
Coastal locations such as Whitmore Bay and Penarth will likely remain slightly cooler than inland areas during the hottest days, thanks to sea breezes.
While temperatures are set to peak on Wednesday, sources vary on the exact figures.
Cardiff Airport is forecast to reach 33°C, but other areas such as Barry Island Pleasure Park could see temperatures climb to 36–37°C due to localised differences.
Experts recommend checking the latest updates on the Met Office app, as the timing and intensity of any thunderstorms could change closer to the day.
The week will start hot, dry, and settled, before a shift later in the week brings the possibility of heavy showers and thunder to close out the working week.
