Cool season: November to February

This is the most popular window, and for good reason. Daytime temperatures sit in a comfortable range, evenings can actually feel cool (bring a light layer if you're heading up to Doi Suthep or Doi Inthanon), and the air quality is generally at its best for the year. It's also when Yi Peng and Loy Krathong — the lantern and lantern-on-water festivals — usually fall, typically in November. Expect this to be the busiest and most expensive time to book flights and hotels.

Hot season: March to May

Temperatures climb steadily from March, peaking around April, which is also when Songkran (Thai New Year) is celebrated with city-wide water fights in the second week of April — genuinely fun if you're prepared to get soaked, disruptive if you need to move around the city with dry luggage. This period unfortunately overlaps with what's locally called "burning season," when agricultural burning and forest fires across the region push air quality down, sometimes significantly. If air quality is a health concern for you, this is the season to research carefully before booking.

Rainy season: June to October

Rain tends to arrive as strong, relatively short downpours rather than all-day washouts, often in the afternoon or overnight. The countryside is at its most green during these months, crowds thin out, and prices drop. Waterfalls in the national parks are at their most dramatic. It's a legitimately good time to visit if you don't mind planning around the occasional storm.

Quick recommendation by priority

  • Best overall comfort: December – January
  • Best value, decent weather: late June or October, at the edges of the rainy season
  • Avoid if air quality is a concern: mid-February through April
  • Want the lantern festival: aim for November, and book months ahead
Good to know

Dates for Yi Peng, Loy Krathong and Songkran are set by the Thai lunar calendar and shift slightly year to year, so confirm exact dates for your travel year before booking around them.