Thailand has three seasons: cool and dry (November to February), hot (March to May), and rainy (June to October). The cool season is the most popular time to visit, with temperatures in the mid-20s°C and clear skies. By April the heat in inland cities can push well past 38°C.
The rainy season is not the disaster some guides imply. Rain usually comes in afternoon bursts rather than all-day downpours, and the countryside is lushly green. Prices drop, crowds thin out, and accommodation is easier to find. If you're mainly interested in temples and cities, the wet season is perfectly manageable.
Northern Thailand
The cool season (November to February) is ideal for trekking around Chiang Mai and Chiang Rai. By March the heat builds. The burning season from March to April also brings haze to the north — air quality can be poor and visibility deteriorates.
Southern Thailand: West Coast
Phuket, Krabi, and the Andaman coast are best from November to April, when the southwest monsoon has passed and seas are calm. The wet season (May to October) brings heavy rain and rough water; many dive operators stop running trips, and some smaller islands effectively close.
Southern Thailand: East Coast
Koh Samui, Koh Phangan, and Koh Tao on the Gulf side follow a different rhythm. Their peak season runs roughly December through August. October and November can be genuinely wet.
Festivals Worth Timing Around
Songkran (Thai New Year, April 13–15) is a nationwide water festival — streets fill with water fights, and most things shut down for several days. It's chaotic, joyful, and hard to ignore. Chiang Mai puts on the most famous celebrations.
Loy Krathong (full moon in November) is the festival of floating offerings — candle-lit lotus-shaped baskets set adrift on rivers and lakes. Combined with the Yi Peng sky lantern festival in Chiang Mai, it's one of the most visually striking nights of the year anywhere in Asia.