Thailand has a tropical climate so it is generally very hot, particularly between March and May with April being the hottest month (30°C/86°F). The monsoon season runs from May/June to October, when the climate is still hot and humid with torrential rains. Rain in the south typically continues until December. The best time for travelling is November to March as the monsoon season is over and the hot temperatures of Thailand’s summer are yet to arrive. The southern islands like Koh Samui are best from June to September where temperatures average around 27/28°C (81/82°F).

Lightweights and rainwear are advised. Informal dress is widely acceptable. Beachwear should be confined to the beach and topless sunbathing is frowned upon. Thailand is quite modest so short or revealing clothes in major cities should be avoided if the goal is to be respectful to the locals. Anything knee-length or longer is acceptable as well as shirts, polos and blouses. Take a pair of good walking shoes or boots for jungle trekking, and long-sleeved tops to protect against mosquitoes.