Temperatures will start to gradually rise over the weekend as high pressure from the Azores builds over the UK.
The warmest conditions are expected from Monday, with temperatures across much of England and Wales likely to peak during the middle to latter part of the week.
Several areas may meet official heatwave criteria if these temperatures persist for at least three consecutive days.
The highest temperatures will be focused across southern and eastern England, where values could exceed 30C widely.
In the north-east of England and eastern Scotland temperatures could reach the mid to high 20s.
Areas on the western side of the UK – such as Lancashire, the Lake District, western Scotland and Northern Ireland – will be exposed to an Atlantic breeze which will act like a natural air conditioner limiting temperatures to the low to mid-20s.
Currently many forecasting models show that the hot spell could persist into the middle of July – although unlikely to reach the record breaking temperatures we saw in June.