Between the Scheldt and the Haine
Hainaut is the most varied province of southern Belgium, running from the French border at Mouscron to the first foothills of the Ardennes near Chimay. The Scheldt flows through Tournai in the west, the Haine through Mons in the centre and the Sambre through Charleroi in the east. This web of rivers, canals and old spoil heaps shapes a lively local climate: Tournai collects only about 730 millimetres a year, while Charleroi receives roughly 861 on around 153 wet days.
Relief explains much of the gap. The west lies at 30 to 50 metres, like the Flemish plain, while the south and east rise towards the Thiérache hills. Houses in Momignies stand at 261 metres, and the average January minimum there drops to just 0.3 degrees, against 1.6 in Tournai. Drive south from the coast and the car thermometer registers that step long before the road signs do.
The old coalfield
Around Charleroi, La Louvière and Binche lies the former mining belt known as the Pays Noir. Slag heaps, headframes and canals dominate the view, and the dark cones store heat on summer days. With a July mean of 22.9 degrees Charleroi belongs among the warmer Walloon cities, while nearby Fleurus, at 157 metres, stays a shade cooler. In built-up valley floors, cold air pools under high pressure in winter and fog lingers well into the late morning.
The Binche carnival and other festivals in the mining towns fall in February or March, when conditions are still unsettled. Showers and bright spells can alternate within the hour, so anyone celebrating outdoors packs rain cover. February brings about 68 millimetres in Charleroi, and April is the driest month at a little over 52. For snow on higher ground, look at Namur and Luxembourg province.
Hills, ponds and the western farmland
Further north, around Ath and Soignies, pasture alternates with limestone quarries, and the Pays des Collines near Ellezelles is among the prettiest corners of the west. Soil here warms faster in spring than on the Ardennes plateau, and oilseed rape flowers weeks earlier. The July afternoon average in Mons reaches 23.3 degrees, and Ath matches it; the difference with Mouscron stays under a degree.
In the south, by contrast, the land climbs with every kilometre and the woods near Chimay look almost Ardennais by October. Anyone living in Froidchapelle at 245 metres sees winters with night lows around 0.3 degrees, more in the manner of the uplands. Rain totals there are higher, at about 840 millimetres, and a March frost is no surprise. Summer thunderstorms like to roll over these hills and break above the forests late in the day.
Floods, heat and summer storms
The rivers of Hainaut are tamer than they appear, but not harmless. After long rainy spells or a quick thaw the Scheldt, Haine and Sambre rise, and low streets in Tournai feel it quickly. Wallonia's hydrometric service publishes live gauge readings, a more dependable source than any forecast when flooding is the question.
In summer, heatwaves can bake the densely built basins around Charleroi and Mons. Nights stay warm because asphalt and brick give heat back. Pollen is part of daily life as well; birch and grasses are covered in our guide Pollen in Flanders and Wallonia. The 14-day forecast for Charleroi helps place such peaks early.
Where to go for the weekend
Hainaut offers outings for every sky: the mining heritage of Le Grand-Hornu, the cathedral quarter of Tournai or a stroll along the Canal du Centre. In sunshine the ponds and woods south of Thuin open up, in rain the museums of Mons are a comfortable fallback. For fresh air, head north through Walloon Brabant or east into the Ardennes.
The map gives a quick bearing: on the Belgium weather map you can see whether a front is sliding from Tournai towards Charleroi and how long the rain will last. That often saves half a day of waiting and points to the best hours for the drive. Local lore says the best weather for Hainaut is a stiff south-westerly: it blows the fog off the canals and dries the Pays Noir quickly after rain.
Sources and further reading
IRM-KMI: Royal Meteorological Institute of Belgium
Waterinfo: river levels and flood situation in Flanders