When is the best time for diving on Koh Tao?

Roughly March to September, when seas are calm and visibility at its best. Diving runs year-round, but October to December brings wind, rain and reduced visibility.

When is the rainy season on Koh Tao?

October to December, peaking in November. Like the rest of the Gulf, Koh Tao stays largely dry through the European summer months.

Can ferries to Koh Tao be cancelled?

Yes — in the November–December monsoon, rough seas occasionally halt crossings from Chumphon and Surat Thani for a day or two. Build slack into travel plans in those months.

When can you see whale sharks at Koh Tao?

Sightings happen year-round and are never guaranteed. Many divers report clusters of sightings in the settled months around March–May and again around September–October.

Best Time to Visit Chiang Mai – Weather & Seasons Guide

Three seasons, and one of them is smoke

Chiang Mai sits in a bowl of hills, and that shapes its year more than the rain does. From November to February the cool season brings dry days in the high twenties and nights that are genuinely cold by Thai standards — ten to fifteen degrees in December and January, cold enough that the guesthouses hand out blankets.

The view from Doi Suthep over the valley

From late February through April the north burns: farmers clear fields and forest across the region, the hills trap the smoke, and Chiang Mai regularly appears near the top of the world's worst air quality readings in March. It is not a rumour and it is not mild. If you have asthma, small children, or a choice of dates, do not come in March.

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In short

Chiang Mai seasons

November–February: cool, dry, clear — the main season
November: the best month of the year, and Yi Peng falls in it
March–April: hot, and burning season smoke, worst in March
May–October: rainy, green and half price; September wettest
Best value: late October and November

November to February, the good months

November is the pick of the year: the rains have just washed the air clean, the hills are still green, the nights are cool and the peak-season prices have not arrived yet. It is also when Yi Peng and Loy Krathong fall — the lantern and float festivals, on dates that move with the lunar calendar, and the busiest week in the city.

December and January are the classic cool-season months: reliably dry, sunny, and cold enough after dark to want a jacket on Doi Suthep. This is high season, so rooms cost the most and the Old City is full. February is still good, though the first haze usually shows up towards the end of it.

Good to know

Planning around the weather

Check an air quality index before booking anything between mid-February and mid-April.
Yi Peng and Loy Krathong move with the lunar calendar — confirm the dates before you book flights.
Songkran in April is bigger here than almost anywhere; brilliant if you want it, unavoidable if you don't.
Nights in December and January are genuinely cold on Doi Suthep — bring something warm.

Terraced hills at Mon Cham north of the city

The rains: green, cheap and underrated

May to October is the wet season, and in Chiang Mai that mostly means heavy afternoon or evening downpours rather than all-day rain. September is the wettest month. The waterfalls run, the rice terraces are luminous, room rates fall by half and the city belongs to the people who live in it.

The one thing to plan around is the roads: mountain routes to Pai, Mae Hong Son and the hill villages get slow and slippery, and a scooter is a worse idea than usual. Late October is the sweet spot — the rain is finishing, the air is as clean as it gets all year, and the crowds have not started.

Month by month

January	Cool, dry and sunny — peak season, cold nights
February	Still cool and dry, haze creeping in late in the month
March	The worst air of the year — hot and smoky
April	Very hot, smoky early, Songkran mid-month
May	Heat breaking, first rains, air clearing
June	Warm and green, afternoon downpours
July	Wet and lush, mountain roads slow
August	Heavy rain, waterfalls at their best
September	The wettest month — quiet and very cheap
October	Rain ending, clean air, brilliant late in the month
November	The best month: clear, green, cool, Yi Peng
December	Cool and dry, high season prices, cold nights

Frequently asked questions

When is the best time to visit Chiang Mai?

November to February, and November above all: clean air after the rains, green hills, cool nights and prices below the December peak.

What is the burning season in Chiang Mai?

Late February to April, when farmland and forest are burned across northern Thailand. The hills hold the smoke in and Chiang Mai's air quality is among the worst in the world in March.

Is Chiang Mai worth visiting in the rainy season?

Yes. May to October is green and cheap, and the rain usually comes as heavy afternoon bursts rather than all day. Mountain roads are the part to be careful about.

When is the Yi Peng lantern festival?

In November, on dates set by the lunar calendar, alongside Loy Krathong. It is the busiest week of the year in the city, so book well ahead.

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Best time to visit Chiang Mai