The Royal Meteorological Institute (IRM) issued an orange alert on Wednesday for storms in the provinces of Hainaut, East Flanders, West Flanders, Walloon Brabant, Vlaams Brabant and in the Brussels Region.
The alert entered into effect at 13:00h and will continue until 4:00 a.m. on Thursday.
A yellow alert is in place for the other provinces.
From mid-afternoon on Wednesday, thunderstorms will move towards the northeast from around the French border, the IRM forecast. These storms could be stronger in the west of the country. There is a strong likelihood of short, sudden bursts of heavy rainfall along with hail and strong gusts of wind.
The possibility of other provinces being upgraded to orange is not to be ruled out, IRM warned.