Soppong sits at 750 metres elevation, which makes it noticeably cooler than the lowland Thai cities — a relief in the hot season and genuinely cold in winter (December to February). The dry season from November to May is the best time to visit: trails are passable, caves are accessible (not flooded), and the air is clear.
The wet season (June to October) brings heavy rain, particularly July and August. The rivers flood and some caves become inaccessible or dangerous. Trails to hilltribe villages can be muddy and difficult. That said, the jungle is lush and beautiful, and there are fewer tourists.
December and January are the coolest months, sometimes dropping below 10°C at night — bring warm clothing if you're visiting then. The light and clear skies in November and February are particularly good for photography in the hills.