A plume of tropical air from the Atlantic Azores Islands will send the mercury rocketing around 15C higher than normal this weekend.
Possible highs of 30C (86F) on Monday will topple a raft of weather records as Britain prepares to roast in the hottest May Day ever.
Thermometers will skyrocket from tomorrow ahead of what is now certain to be the warmest weekend of the year so far.
Families heading away have been warned to prepare for delays with millions of cars expected to hit the roads over the three-day break.
Britons will make around 2.9 million journeys tomorrow with 2.5 million expected on Saturday, 1.27 million on Sunday and 1.9 million on Monday, according to the RAC.
A temperatures start to rise, forecasters say early signals show heatwave conditions holding out into the middle of May.
The sweltering prediction has prompted bookies to take the axe to a raft of monthly and seasonal summer odds ahead of records tumbling.
Highs of between 26C (78.8F) and 30C (86F) on Monday will bring the hottest May Day in history beating the 23.6C (74.48F) maximum set in 1999.