The current month is on course to be the warmest February since records began as record-breaking temperatures start to ease off.
Scattered showers on Thursday will bring an end to the “wall-to-wall” sunshine enjoyed during the recent hot spell, which saw new winter record temperatures set on two consecutive days.
The previous warmest February was in 1998, when the average maximum daily temperature was 9.8C (49.64F).
With just one day to go before the beginning of March, this year’s maximum daily average has already reached 9.9C (49.82F), the Met Office said.
Forecaster Becky Mitchell said it would be “exceptional” to beat the 1998 record given the chilly start to the month.
She said: “At the moment, the current average is 9.9C and of course we have got just one more day of February to go, so it looks like we are on track to be the warmest February on record.”
Ms Mitchell added: “It was really quite cold at the start of the month – it’s pretty exceptional to have caught up with the 1998 one.”
Experts said climate change is heating up the whole weather system and making extremes more likely.
February’s exceptional conditions have seen fires at Arthur’s Seat in Edinburgh, on Saddleworth Moor in West Yorkshire and in North Wales, Sussex and Lancashire.
The warmest winter temperatures on record were measured on Monday and Tuesday as temperatures beat the previous record of 19.7C (67.4F) in Greenwich, south-east London, in 1998.
Thursday is predicted to stay mild, with cloudy skies and highs of 14C (57.2F) forecast in London.
But it will be more unsettled than the previous clear days, with fog expected in the morning and “possibly heavy and thundery” showers moving east across England and Wales.
Friday will see some heavy rain in western parts of the UK, and the unsettled weather is to continue “right through the weekend”, Ms Mitchell said.
The conditions will be a “big contrast” to the sunny start to the week, she said, adding: “It will be wet and windy for the whole of the UK, and very strong winds across many places, and we could even have gales in the west.”