Average daily temperatures in September
September is one of the wettest months in Thailand, particularly in the south. Bangkok experiences temperatures between 78°F (26°C) and 90°F (32°C) with about 12 inches (300mm) of rainfall. Chiang Mai remains cooler, with highs of 87°F (31°C) and lows of 72°F (22°C).
Phuket, Krabi and Samui are drenched with up to 14 inches (360mm) of rain, but temperatures still range from 77°F (25°C) to 87°F (31°C). Sunshine is reduced to around 4-5 hours per day.
September is ideal for those looking to avoid crowds and take advantage of lower prices, but be prepared for frequent rain. Inland regions like Chiang Rai and the Golden Triangle offer a cooler, less rainy alternative to the coast.