West Flanders and Hainaut have been placed on code red for Tuesday since there is at least a 65% risk of highs above 40 degrees in a quarter of the two provinces, the Royal Meteorological Institute (IRM) announced on Monday evening on Twitter.
The code is in effect from 18 July at midnight to 20 July at the same time.
On Tuesday, the heat will be oppressive with maximums of 34 to 39 degrees, and locally 40 degrees in the west/south-west of the country, IRM warned.
