Temperatures will reach 36°C this weekend before finally raining at the beginning of next week, but experts predict it will not be enough to relieve the drought.
Following months of unusually warm and dry weather, the National Drought Group declared drought status during a meeting on Friday.
The Met Office predicts sunshine for much of the nation on Saturday, with any low cloud and fog dissipating fast in the morning.
It will be hot or extremely hot, especially in central and southern England, where temperatures might reach 36°C.
Heatwave in the UK hits 36C
Carl Court/Getty Images
The heat will persist for most of the country on Sunday, although heavy rains are possible farther north in Scotland and Northern Ireland, as per iNews.
An amber heat warning is in effect for parts of England and Wales on Saturday and Sunday, and a yellow thunderstorm warning is in effect for Scotland and Northern Ireland on Sunday, moving south to England and Wales on Monday.
The Met Office's Nicola Maxey warned of the possibility of flooding next week.
"On Monday, the thunderstorm warning is in effect from 6 a.m. to midnight and includes much of England, all of Northern Ireland, Scotland, and Wales," she added.
The weather is expected to improve starting Wednesday, and "we will be freed of this hot humid air and return to a milder regime but not chilly."
Temperatures are expected to be in the mid to high 20s, with temperatures in the low 20s further north. This is closer to the August average.
Despite the rain, John Curtin, the Environment Agency's executive director for local operations, says it will not end the drought that is now afflicting portions of England.
Mr. Curtin told BBC Radio 4's World at One: "Basically, it's a signal that this isn't a regular summer anymore, therefore water will be an issue for months to come."
"While some locations stay dry, hit-and-miss thunderstorms will develop from Sunday night and on Monday, and may cause inconvenience in spots," the national meteorological service said, as per Express.
Thunderstorms may hit Central, Tayside & Fife, South West England, North East England, Northern Ireland, Grampian, Wales, West Midlands, Highlands & Eilean Siar, London & South East England, North West England, East England, Dumfries, Galloway, Lothian & Borders, Yorkshire & Humber, Esat Midlands, and Strathclyde.
Extreme weather conditions could swiftly flood homes and businesses, causing damage to certain structures from floodwater, lightning strikes, hail, or high winds.
The Met Office has advised that when floods or lightning strikes occur, railway and bus services may be delayed or canceled.
Spray and flash floods may also cause challenging driving conditions and road closures.
Finally, there is a tiny possibility of power outages and the loss of other services to certain homes and businesses.
While some areas may be spared, thunderstorms are expected to become more widespread as the day progresses.
Storms are expected to begin in Northern Ireland and parts of Scotland by early Monday, before spreading to portions of England and Wales by late morning and into the afternoon.
Storms from the west should begin to clear later. It is possible to get 20-30 mm of rain in an hour, and up to 50 mm in three to six hours.
Hail and lightning are also possibilities.
According to the Met Office, thunderstorms develop owing to the presence of cumulonimbus clouds, sometimes known as 'The King of Clouds.'
These are the only clouds that can produce hail, thunder, and lightning, and they have menacing-looking multi-level clouds that reach far into the sky in towers or plumes.
They are related to extreme meteorological conditions such as strong rains, hail storms, lightning, and even tornadoes.
