Wednesday afternoon will be very hot and sunny, with temperatures between 31°C and a tropical 35°C, according to the Royal Meteorological Institute.
This is raising the prospect of a new heatwave in the coming days, Belgian weather experts warn.
Wednesday evening and overnight will remain very mild, with minimum temperatures of 17°C to 22°C.
Thursday will again bring plenty of sunshine, although some cumulus clouds will develop inland during the day.
A few thunderstorms are possible in the south-east, but any activity is expected to remain limited. Maximum temperatures will range from 23°C on the coast to 32°C in the east.
Friday will be partly cloudy, with a chance of a few showers in the far west and east. Temperatures are expected to reach up to 29°C in the centre of the country.
The weekend will begin on Saturday with more cloud and a slight chance of light rain. Highs will be around 27°C.
It will turn warmer again on Sunday, with temperatures rising to 30°C.
Apart from Saturday, temperatures are expected to hover around the 30°C mark in the days ahead, making the likelihood of a new heatwave a real possibility.
Although temperatures are expected to stay below 30°C on Friday and Saturday, the yellow heat warning will remain active everywhere except along the coast until Sunday.
