The Met Office says that temperatures could climb as high as the mid-30s this week and parts of Britain could be hotter than Jamaica and Portugal.
Friday is on course to be the hottest day of the year, with temperatures steadily rising until then.
Monday is expected to bring sunny spells for England and Wales ahead of hotter temperatures in mid-week, while Scotland and Northern Ireland can expect cloudier conditions with light rain.
And once the warm weather sets in, it could become a feature of the summer with heatwaves also likely over the coming months, and one meteorologist hailing a turning point after a disappointing start to the year.
Steven Keates of the Met Office said: “There’s not been much in the way of exceptionally warm days or hot days yet this year, but that is set to change.
“We’re set to see probably a brief spell of hot weather at the end of this coming week.”
Temperatures are currently forecast to reach 32C in the south-east on Friday but Mr Keates added: “It could possibly be a little hotter than that… mid-30s are possible.”
Should mercury levels creep into the 30s this week, Britain would likely be hotter than Portugal, Jamaica, Costa Rica, the Canary Islands and Cyprus.
It would also mean the hottest day of the year so far, eclipsing the record of 27.5C set in mid-May at Heathrow.
“We should beat that comfortably on Friday and potentially exceed it, or get very close to it, on Wednesday and Thursday as well,” Mr Keates said.
The meteorologist added that heatwaves - three consecutive days of high temperatures - were possible between June and mid-September.
"We think at the moment it will be warmer than average with an increasing likelihood of heatwaves," he said.
"There have been no heatwaves so far this year... the greater likelihood is that it's going to be the further south, south east, you are."
It comes as UK tourists heading to Spain or Portugal have been warned of intense weather conditions as temperatures soar.
The mercury could top 40C in some Spanish towns, with no sign of the heatwave settling in the next few days.
Intense conditions are expected in Costa del Sol, as well as the Balearic and Canary Islands, up until the end of next week.
An orange weather warning has been issued with highs of 44C forecasted in Andalusia.
UK forecast for the next 5 days
Today:
Sunny spells and fine weather across England and Wales. Cloudier with light rain in Scotland and Northern Ireland, with heavier showers in northern Scotland.
Tonight:
Chilly in the south and cloudy in the north-west, where there could be some patches of rain. Most areas will be largely clear.
Tuesday:
Mainly dry with varying amounts of cloud punctuated by sunny intervals. Scotland and Northern Ireland could be cloudy with areas of rain.
Outlook for Wednesday to Friday:
Temperatures rising to potentially hot levels by Friday. The north-west will continue to experience cloud, rain and breezy conditions.
