Thailand weather, region by region — and why the rainy season isn't what you think.

Cooler highland evenings, a dry burning season to plan around.

Follows the mainland three-season pattern closely, with the most distinct cool season of anywhere in Thailand — mountain evenings can feel genuinely cool, even chilly at altitude. One regional quirk worth knowing: February to April is often hazy from agricultural burning, which can affect air quality and mountain views more than rain does. Rainy months (roughly June–October) bring lush, misty landscapes and fewer crowds at temples and trekking routes.

The classic three-season year; short evening downpours in the wet months.

Bangkok and the central plains are the textbook three-season case: a comfortable cool season (Nov–Feb), a hot and humid March–May, and a wet season from roughly May to October where a daily late-afternoon shower is common but rarely lasts long. City life continues normally through the rainy season — just carry a light rain jacket and expect the odd flooded street after a heavy burst.

Runs opposite to the rest of the country — wettest around October–December.

This is the zone that surprises people: the Gulf islands face the opposite monsoon to the rest of Thailand, so their wettest months are roughly October to December, while the mainland's June–September monsoon barely touches them — that stretch is often one of the sunniest times to visit Koh Samui. If travelling in November or early December, build in flexibility for short but sometimes heavier showers and occasional rough boat crossings.

Follows the south-west monsoon; roughest seas May–October.

Broadly follows the mainland's monsoon timing — wet season roughly May to October, dry and sunny November to April. The main practical impact here is at sea rather than on land: the south-west monsoon can bring choppier waters and stronger currents, so island-hopping, diving and snorkelling trips are easiest to plan November–April, and some smaller boat routes reduce service or pause in the wettest weeks.