The rainy season lasts from July to October and is dominated by the southwest monsoon, during which time rainfall in most of Thailand is at its heaviest. However, like the “cool” season, the name “rainy season” is slightly misleading. While it certainly does rain during this season it’s more likely to consist of flash-flood afternoon downpours than a continual drizzle for days. If you can bear the heat and humidity, the weather in Thailand is typically sunny throughout the rainy season, but when the rain comes, it’s fast and it’s furious.