The Walloon plateau
Walloon Brabant is the smallest province in the country and lies on a broad loess plateau south of Brussels. There are no mountains, but the high ground rises gradually: Tubize stands at 52 metres, Wavre at 60, Nivelles and Genappe at about 100 to 107, Walhain at 156. With each step up the wind grows, nights cool and spring and autumn shift by a few days.
The climate is balanced and free of extremes. January in Wavre brings an average daytime high of 6.3 degrees and a night-time low of 1.5; July afternoons reach 23.8. In Walhain, the highest of these towns, the January night drops to 1.0 and the July heat stays at 23.2. Annual rainfall is around 860 millimetres in most places, 888 in Genappe.
Waterloo and the wide plain
On the plateau south of Brussels the battle of Waterloo was fought in 1815, and the Lion's Mound is about 43 metres high and rises above the fields. The open expanse is weather-sensitive: westerly wind sweeps unimpeded across wheat and beet, and climbing the steps to the mound you feel gusts that look like a light breeze at the bottom. The plain is therefore good ground for wind turbines and glider pilots.
Around Braine-l'Alleud and Lasne the land meets the Sonian Forest. In autumn mist lies over the meadows, and early frost whitens the plants before the sun thaws them. The plain copes well with rain, since loess stores water, though after long wet periods streams overflow. The Senne rises not far off and passes Tubize and Rebecq.
Wavre, the Dyle and Louvain-la-Neuve
The Dyle crosses Wavre, capital of the province, and Ottignies-Louvain-la-Neuve, the young university town founded only in 1970. Along the river, water can rise after heavy rain in May or June and flood meadows and underpasses. The municipalities are well prepared, but individual roads are closed again and again in severe weather.
In summer especially, thunderstorm cells approach from the south-west. The plain gives them room, and they often build over the fields of Jodoigne in the Brabant Hesbaye before reaching Wavre. The 14-day forecast for Wavre shows the tendency; those sitting outdoors in the evening also check the weather map. Jodoigne records 23.6 degrees by day in July and 875 millimetres of rain a year.
Villers Abbey and nature
In the woods near Tilly lies Villers Abbey at 102 metres, a ruin that impresses even without a roof. Visiting its passages in rain, you see water running across the walls, and in mist the place feels lifted from a tale. A small stream, the Thyle, crosses the grounds, and its level rises in winter.
The Brabant country is fertile, and agriculture sets the year. Sugar beet, wheat and rape need warmth in April and rain in June. In Grez-Doiceau at 48 metres July reaches 23.9 degrees, and harvests there often ripen earlier than in higher municipalities. In spring birch and grasses release pollen that the wind carries far; our guide Pollen in Flanders and Wallonia helps recognise the peak phases.
Neighbours and planning
To the north the province borders Brussels and Flemish Brabant, to the south Hainaut and Namur. Driving south from Nivelles you see the landscape rise into hills in Hainaut and clouds banking up. Heading east towards the Hesbaye, you meet drier weather.
For leisure and planning, short-range forecasts are the most useful. A walk at Lac de Genval or a cycling day on the Dyle towpath works out if you check air and wind in the morning. With frost risk in April, garden owners watch night temperatures, and in high summer thunder decides whether the open-air party goes ahead. Drivers on the N25 or the motorway towards Namur in winter occasionally meet blowing snow on the open plateau that hardly reaches Brussels. Gritting crews are therefore quick to respond, and winter-sports fans have only a short drive south to the Ardennes.
Sources and further reading
IRM-KMI: Royal Meteorological Institute of Belgium
Waterinfo: river levels and flood situation in Flanders