The upland south of the Ardennes
Luxembourg province is the largest and least densely populated in Wallonia, and its weather ranks among the roughest in Belgium. Plateaux, forests and deep valleys alternate, and altitude makes the difference: Bastogne stands at 510 metres, Libramont-Chevigny at 508 and Arlon at 420. January in Bastogne means an average night-time low of minus 1.6 degrees and a daytime high of only 2.9, a near-permanent frost mood that Ostend hardly knows.
Summer stays moderate too. July highs in Bastogne average 20.4 degrees, whereas Virton in the south reaches 22.5 and Aubange on the Grand Duchy border 22.2. The contrast between the cool Ardennes plateau and the milder Gaume is the defining feature of the province, and it explains why a forecast for the north seldom fits the south.
Snow, frost and slippery roads
Winter weather here is not an event but the baseline. Libramont-Chevigny receives over 1,040 millimetres a year on 163 days, Vielsalm on as many as 169. A large share falls as snow in winter, especially on the 652-metre ridge of Baraque de Fraiture, where flakes can fly while rain falls down in the valley at La Roche-en-Ardenne. Which places are most reliable is described in our guide Snow in the Ardennes.
Ice often matters more than depth. Freezing rain and fog on the high plains turn the N4 and the motorway towards Arlon into a hazard, and wind builds drifts on open stretches. Anyone arriving from Brussels in winter should check not only the forecast for the destination but also the one for the plateau in between. Conditions near Bastogne are often much harsher than in Marche-en-Famenne, which stands at 200 metres.
Rivers, castles and natural sights
The Semois winds in tight loops through slate, past Rochehaut at 340 metres and the castle town of Bouillon in the gorge. Down there the weather feels different: Bouillon lies at about 226 metres, stays a little milder in winter and falls into shade early on summer evenings. The Ourthe runs through Durbuy, which likes to call itself the smallest city in the world, and on past La Roche-en-Ardenne, where a ruined castle perches on a crag.
After heavy rain these rivers rise quickly. The valleys are narrow, water arrives from dozens of streams, and floods can reach roads and campsites within hours. Kayakers on the Ourthe or the Lesse therefore check the gauge on Wallonia's hydrometric pages before launching. Fog clings to the valleys until late morning while the heights above already enjoy sunshine.
Gaume, the mild corner
In the far south the Gaume opens out, a stretch of country whose climate recalls Lorraine. Virton, Étalle and Florenville lie between 250 and 357 metres, and summers are clearly warmer than in the north. Rainfall is a little lower than on the heights: Virton records 914 millimetres and Arlon 917, with fewer rainy days than on the plateau.
This is also thunderstorm country. In summer, heat storms break over the southern rim and can drop large amounts of rain quickly. After hot days look at the weather map, because cells drift in from France across the border. The area suits cycling on old railway beds, as long as the sky to the west stays bright.
Planning your trip
Visitors to the province plan best with two forecasts, one for the height and one for the valley. The 14-day forecast for Bastogne gives the guidance that decides between snow tyres in winter and a rain jacket in summer. To the west lies Namur, to the north-east Liège with the plateaux of the High Fens.
The beauty of the landscape rewards anyone with a little weather sense. Beech woods turn in autumn, broom blooms on the slopes in spring, hoar frost glitters on the pastures in winter. And those who prefer dry feet will find April, with roughly 65 millimetres, the driest month. In the autumn months game moves through the woods, and walkers stick to marked paths during the hunting season. Early snowfalls from October are no rarity on the heights.
Sources and further reading
IRM-KMI: Royal Meteorological Institute of Belgium
Waterinfo: river levels and flood situation in Flanders