You should think that in a small country like Belgium the weather would be the same in all places, but that's not true: We have such a lot of microclimates here that there can be a difference of several degrees within a distance of a few kilometers.
Have a look at different stations as Willebroek doesn't have an own one one the net:
Antwerp (20 km north of Willebroek)
Hove (17 km northeast)
Sint Niklaas (20 km northwest)
Brussels (27 km south)