Bookmakers Ladbrokes put the odds of exceeding the highest temperature ever recorded in the UK at 7/1.
Thermometers climbed as high as 38.5C (101.3F) in Kent in 2003, but that could be beaten this year.
Spokesman Robin Hutchison said: "If the forecasters are to be believed the thermometer could hit treble figures more times than England's batsman this summer.
"A nationwide gamble could seriously burn the bookies and see profits evaporate overnight."
The Met Office has issued a "heat health" warning for this week, with night time temperatures in some areas due to remain as high as 18C (64.4F).
It is expecting some of the hottest days of the summer so far and said there is a 60 per cent chance of temperatures reaching 32C (89.6F).
The Department of Health said the elderly and young children were most at risk from heat stroke in hot weather.
It advised staying out of the sun, avoiding going out in the hottest part of the day and strenuous activities, and drinking plenty of water.
This is what we have been waiting for for the last two years. We have many specimens where we cannot decide if they have virus or are under extreme stress due to the foul weather we have had the last few years. We need a year of good light to establish if they have virus or not.
In the meantime we have watered and fertilized the Canna beds so well that the plants are sitting in a soil soup, so they will have the water and nutrients to get the worlds best starch machine working overtime! Once the heatwave is over we will stop watering and allow the soil to dry out more and allow normal oxygen levels down at the roots. We can only do this as most Canna cultivars have an aquatic ancestor and they are happy to obtain their root oxygen from the high levels of water we have introduced.