As the heatwave moves across the country, French capital Paris is expected to reach 39 degrees Celsius (102.2 degrees Fahrenheit) on Tuesday.

In the UK -- where Monday's temperatures reached 38.1 degrees in eastern England's Santon Downham, making it the third hottest day on record -- officials warned things would likely get worse.

The head of the UK#39;s Met Office said the country could experience the quot;hottest dayquot; on record Monday.

The head of the UK's Met Office said the country could experience the "hottest day" on record Monday.

Tuesday is "expected to be even hotter," according to the Met Office's CEO, Penelope Endersby.

"It's tomorrow that we're really seeing the higher chance of 40 degrees and temperatures above that," Endersby told BBC Radio on Monday.

"Even possibly above that, 41 is not off the cards. We've even got some 43s in the model but we're hoping it won't be as high as that."

Belgium's Royal Meteorological Institute (KMI/IRM) has issued a "code red" weather warning for heat in two provinces on Tuesday, forecasting temperatures up to 40 Celsius in the west and southwest.

"With such very high temperatures certain measures will be necessary: drink regularly, wear lighter clothes, spend the day in cooler rooms, monitor the state of your health regularly, eat easily digestible food (and in smaller portions), keep doors and windows closed to keep the heat out. Pets and animals also need extra care," it warned residents.