Myanmar has three distinct seasons, and the difference between them matters a great deal.
Cool and dry season: November to February
This is the best time to visit. Temperatures are comfortable — warm during the day, cooler at night, particularly in highland areas like Kalaw and Inle Lake. The skies are clear and the light is good. December and January are peak season; book guesthouses and domestic flights in advance. February is excellent and slightly less crowded.
Hot and dry season: March to May
It doesn't rain much, but the heat is intense, regularly exceeding 40°C in lowland areas like Bagan. Bagan in March and April is genuinely punishing — exploring temples in the midday heat is not enjoyable. If you're going during this period, start very early and be back inside by 10am. Inle Lake and highland areas are more manageable.
Monsoon: June to October
Heavy rainfall daily, with grey skies and flooded roads. Some areas become inaccessible. That said, the landscape turns spectacularly green, the light in the late afternoon can be beautiful, and tourist numbers drop sharply — which means you'll often have Bagan's temples to yourself. Accommodation prices fall. It's a real option if you don't mind the rain. Inle Lake is particularly atmospheric in the monsoon. Avoid Rakhine coast routes during this period.
The Thingyan water festival, which marks Burmese New Year, falls in mid-April (usually 13–17 April). It's a remarkable spectacle — the whole country drenches itself with water for four days. Transport grinds to a halt and most businesses close, so plan accordingly.