Best month to arrive in SE Asia
A twelve-month heatmap per destination blending heat, rainfall, haze risk and major holidays. Green months are the calm windows. Red months are the ones to skip.
Reading the heatmap
Each row is one city. The twelve cells are January through December. The face inside each cell summarises the month at a glance: laugh (best), smile (good), meh (ok), frown (tough), angry (avoid). The letters underneath flag the specific gotcha (Haze, Typhoon, Festival). The thin black outline marks this month, so you can see whether you're standing in a green window or a red one. Hover any cell for the exact comfort score and details.
The "Best in X" line at the top right of every row spells out why a month wins or loses, so you don't have to hover every cell to understand the shape of the year. Each row has its own country and city dropdowns. The + Compare button next to the first row adds a second picker just below it; click it again to add a third, and so on. The ✕ on each comparison row removes it.
How the score is built
For each city and month we combine four monthly normals into a single 0-100 number behind the face icon.
Heat
Daytime high. Comfort is roughly 27-30°C. Every degree above 30 costs 5 points, with extra flat penalties past 34°C (+10) and 36°C (+10). Below 27°C gives a small bonus, which is what surfaces Hanoi winters and the Vientiane December sweet spot.
Rain
Millimetres per month. 100 mm is neutral. Every 50 mm above 100 costs 8 points, with an extra flat +10 past 300 mm (true monsoon flooding, not just afternoon downpours). Manila in August at 485 mm is what triggers the deep red.
Haze
AQI and burning-season windows. The peak window costs 50 points, which alone is enough to drag a month into Avoid territory. Chiang Mai Feb-Apr, Phnom Penh Jan-Mar, KL Sep-Oct. Shoulder months cost 18.
Typhoon
Philippines only. Peak Aug-Sep costs 42 points, the shoulder months cost 18. Reflects the multi-day flight disruption and flash flooding that Manila routinely sees in those months.
Festival
Songkran, Tết, Nyepi, Holy Week, Khmer New Year, Hari Raya, Chinese New Year. A flat 6-point penalty for the logistical pain of arriving during a mass-closure week.
The numbers are long-term climatic averages, not a forecast. Use them to decide which month to fly, then check the news and live AQI closer to the date.
For within-country detail (Chiang Mai in March vs Phuket in March, Hanoi in February vs Da Nang in February) see the country pages: Thailand, Vietnam, Indonesia, Philippines, Malaysia, Cambodia, Laos, Bali.