Saint-Denis (Reunion) weather in December

Forum posters describe March in Réunion as still within the rainy and cyclone season (which runs roughly December through March), genuinely unpredictable - a trip could see a lot of rain or largely blue skies, with cyclone activity itself impossible to forecast season to season. Posters consistently point to Réunion's roughly 100 microclimates as the key to navigating this: the west and southwest coast run driest, while the east coast and mountains run wettest, meaning if it's raining in one spot you can often find dry conditions elsewhere on the same day, cyclones and major depressions aside. Saint-Denis sits on the island's north coast, a zone posters don't single out as either the driest or wettest, sitting between those two extremes. Posters generally rate March as toward the tail end of cyclone season but still genuinely rain-prone for Saint-Denis, with real day-to-day and location-to-location variability across the island worth planning flexibly around.

Forum posters consistently name the June-through-November stretch as the best window to avoid Reunion Island's heaviest rain, placing September squarely within that favorable period. Posters are also direct that the island has over 100 microclimates, so conditions can vary sharply by location - rain is consistently described as less likely on the west coast than the east, a distinction that applies to Saint-Denis on the island's north coast as much as anywhere else. Posters generally rate this dry-season window as good for exploring by car and for hiking, with September sitting comfortably inside the more reliable half of the year rather than the wetter cyclone-season months.