As Britain heads for a sweltering weekend, bookmakers William Hill have cut the odds of temperatures this summer reaching 100 degrees Fahrenheit from 8/1 to 4/1.
The odds are the shortest the firm has quoted so early in the year for over quarter of a century, a spokesman said.
The odds on the British record of 101.3F being broken in 2007 are 8/1. That mark was set near Faversham, Kent, in August 2003.
"The sums of money we are taking on the temperatures reaching 100F are unprecedented," said the spokesman. "We have already taken several four-figure bets and we are now the shortest price we have ever been in April.
"If the level of interest continues, you could see a possible industry payout of a million pounds if temperatures hit the golden mark."
The latest Met Office forecast for summer, issued on Wednesday, said summer is likely to be warmer than normal, exceeding the 30-year average of 57.38F.
"Throughout the summer we can experience periods of very hot weather which has implications for people's health," it added on its Web site, although it did not forecast possible top temperatures.
Its next summer forecast will be issued on May 1.
Meanwhile temperatures in the southeast this weekend are expected to hit 75 to 77F, according to forecasters Meteogroup UK, some 15 degrees above the seasonal average and hotter than Ibiza or Barcelona.