Chiang Mai's best weather by a wide margin: cool mornings, warm dry afternoons, and the lowest rainfall of the year. It's also when everyone else has the same idea, so the Old City and Doi Suthep get genuinely crowded and hotel rates climb to their highest point of the year. If you want these months, especially around November's Yi Peng lantern festival, book well ahead.

This tier covers two very different halves of the year. February through April is still technically dry season: hot, and increasingly hazy from agricultural burning, but real rain stays rare. May, September, and October sit on the other side of the monsoon: expect genuine rain, usually as a heavy but short afternoon downpour rather than an all-day washout, so mornings are typically clear for temple visits and sightseeing. Either way, hotel prices sit well below peak-season rates and the crowds thin out noticeably.

The wettest stretch of Chiang Mai's year, with rain most days and the countryside around Doi Suthep at its greenest. That doesn't mean writing off a summer trip. Showers are usually intense but brief, mornings are often dry, and you'll find the lowest hotel prices and thinnest crowds of the year. Pack a proper rain jacket, keep outdoor plans flexible, and check the afternoon forecast before you head out.