A torrent will lash the nation today just days after June was confirmed by experts as the hottest on record.
Tuesday is forecast to see heavy rain in many parts across the south with showers expected across the country.
The Met Office said: "Rain, occasionally heavy, across the south will only slowly clear eastwards later. Cloud and rain also affecting parts of Scotland and Northern Ireland, with sunshine and showers elsewhere."
And temperatures will also be cooler than they have been in recent weeks with the south east the warmest area but with high temperatures around 20C by late afternoon.
The environment agency currently has one flood alert in place for Somerset Coast at Porlock Weir.
It comes after June was confirmed as the hottest on record by the Met Office.
June's average mean temperature of 15.8C beats the previous record of 14.9C but Met Office has stressed this is a warning climate change is having a huge impact.
Paul Davies, Met Office climate extremes principal fellow and chief meteorologist, said: "The background warming of the Earth's atmosphere due to human induced climate change has driven up the possibility of reaching record high temperatures.
"Using our... climate projections, we can also see that there is a difference in the frequency of these sorts of extremes depending on the emissions scenario we follow in the future.
"By the 2050s the chance of surpassing the previous record of 14.9C could be as high as around 50 per cent, or every other year."
Meanwhile longer range forecasts have predicted better weather ahead.
The UK could see a 28C scorcher by the weekend, gradually rising from 20C on Wednesday.
And the Southeast could be particularly warm by the end of next week, according to the Met Office.
UK weather forecast
Today:
A mixed day today, with showers or longer spells of rain in places. The rain could be heavy at times for southern counties of England in particular. Winds lighter than Monday, but still on the cool side for early July.
Tonight:
Rain, heavy at times, will clear from southeast England through the evening and into the early hours. Elsewhere will see a mix of clear spells and scattered showers.
Wednesday:
Sunny spells and scattered showers. A few may be on the heavy side, most likely across southeast England and the far northwest of Scotland. Feeling slightly warmer for many.
