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The weather in Thailand tends to be hot and humid year-round, and regional patterns diverge more than newcomers expect. The monsoon – a seasonal wind that delivers heavy rains – will quickly become part of your daily calculus here.
The best way to think of Thailand’s climate is to divide the year into three seasons: cool and dry from November to February, scorching from March to June, then wet from June through October. The south follows a different rhythm, with wet and dry seasons that are split by coast. The west coast, around Phuket and Krabi sees peak rainfall from May to October, similar to the north. The east coast – Koh Samui and Koh Phangan – gets drenched from October through December.
The north offers the coolest temperatures, with heat building as you head south. Northern mountain areas can dip to 68°F (20°C) at dawn during the cool season, although daytime temperatures climb far higher. The hot season now regularly exceeds 100°F (38°C) across most regions. Bangkok’s concrete sprawl makes it feel several degrees hotter – a factor for professionals based in the capital. Many internationally mobile workers move to Chiang Mai from November to January, then shift to the coast before the northern burning season takes hold.
Air quality deserves serious consideration. From January to April, agricultural burning in the north sends pollution levels soaring – Chiang Mai and Chiang Rai regularly hit hazardous readings above 200 AQI. Most foreign residents head south during these months. Bangkok faces its own smog season from December to February. A high-quality HEPA air purifier has become standard equipment for new arrivals. The best time to relocate is in November or December, so you can settle in during pleasant weather before the March heat arrives.
Expats should endear themselves to their umbrellas during the rainy season. Brief downpours render Bangkok streets impassable for hours – a reality that has reshaped commute times and property decisions. The south receives roughly double the rainfall of central and northern Thailand, and flash flooding poses risks even in drier areas. Make sure to check flood risk maps before signing a lease.