From Wednesday the southern half of the UK will see temperatures reach the mid 20s and by Friday the warmer weather will peak.
Met Office Chief Meteorologist Matthew Lehnert said, “There is a Met Office rain warning in force for northern England and northern Wales today as a low pressure system eastwards moves across the country.
“Within the warning area, many places will see 20-30mm of rain, with a few isolated spots possibly seeing around 60-80mm of rain over the course of the warning.
“It will be drier for many by Tuesday, as the low pressure moves off into the North Sea.
“Parts of Scotland will continue to see frequent showers, with around 30mm of rain possible over a few hours for Glasgow and Edinburgh. Elsewhere will be largely dry with cloud and sunny spells for many.”
Deputy Chief Meteorologist Dan Harris added, “A general warming trend is expected through much of this week, as the weather settles down for a time.
“Whilst some southern areas are already likely to reach the mid 20s by Wednesday, it’s not until Thursday that the warmer weather will become more widespread, with parts of Scotland also reaching the low 20s.
“Most places will be dry with sunshine, although some early mist and low cloud could mean a slow start for some areas.
“We are likely to see the warmest weather on Friday and Saturday, with low to mid 20s widely and a peak of 29C most probable in the southeast; at this stage the odd 30 Celsius here on Friday cannot be ruled out.
“A frontal system arriving into the west and southwest later on Friday, which could be preceded by thunderstorms, does complicate matters somewhat; after a very muggy night in the southeast overnight into Saturday.”