The best time to visit Kanchanaburi is November to February, the cool dry season, when temperatures are comfortable (around 25–30°C by day) and rain is unlikely. March and April are hot — temperatures often exceed 40°C and are uncomfortable for sightseeing. The rainy season runs from May to October; while Erawan Falls is at its most dramatic in October, flooding can make some roads to national parks impassable.
The River Kwai Bridge Festival takes place in late November or early December each year, with a sound and light show along the river and a small fairground. It is a lively time to visit, though accommodation gets booked up quickly.