When is burning season in Chiang Mai?

In our data, smoke builds from late February, and the average of four seasons (2023 to 2026) peaks in the weeks of 12 to 18 March and 2 to 8 April. Each season differs: the worst two weeks were 2023: 5 to 18 March; 2024: 1 to 14 April; 2025: 19 March to 1 April; 2026: 2 to 8 April and 16 to 22 April.

Is all of February to April bad?

No. The chart shows the weeks as a relative index, where each season's worst week is 100. Some weeks sit far below the peak, and the peak week moved between mid-March and mid-April across the four seasons. The index shows timing only, not how high the levels are.

Where do nomads go instead?

For February to April we compare the best-scoring place in each region from our weather data: the Andaman coast, the Gulf islands, Sri Lanka's south coast, Da Nang and, in April, Bali's Uluwatu. See the cards above for each month's score, day high and rainfall.

Which months are better for Chiang Mai?

From our weather data: November to January has day highs of 27°C to 29°C (January 27°C with 26 mm of rain). May is hotter (34°C) and wetter (183 mm of rain in May), and the last weeks of May sit low on the smoke chart. Our weather score does not include air quality, so it rates February and March highly. Use the chart above for smoke timing.

How reliable is this data?

The smoke index comes from a global air-quality model, not from ground stations, and reads low on bad days. We use it for timing, which weeks are worse. For actual levels, see the station figures in "How bad, really" above.

Chiang Mai Burning Season: When the Air Is Bad, Week by Week, and Where to Go Instead

Week by week: when the smoke is worst

Each thin line is one season (2023, 2024, 2025, 2026), scaled so that season's worst week is 100. The bold line is the average of the four. The shaded weeks are the average's worst two.

Relative smoke level (worst week of the season = 100). 1 January to 27 May.

20232024202520264-season averageaverage's worst 2 weeks

Week starting	Average index (0 to 100)	In a season's worst 4 weeks
1 Jan	49	0 of 4
8 Jan	49	0 of 4
15 Jan	46	0 of 4
22 Jan	54	0 of 4
29 Jan	54	0 of 4
5 Feb	53	0 of 4
12 Feb	55	0 of 4
19 Feb	58	0 of 4
26 Feb	61	1 of 4
5 Mar	73	1 of 4
12 Mar	77	3 of 4
19 Mar	68	1 of 4
26 Mar	76	3 of 4
2 Apr	82	3 of 4
9 Apr	72	2 of 4
16 Apr	69	1 of 4
23 Apr	61	0 of 4
30 Apr	49	1 of 4
7 May	43	0 of 4
14 May	36	0 of 4
21 May	28	0 of 4

Weeks are 7-day blocks counted from 1 January, so the dates shift by a day in leap years. Weeks with fewer than 5 days of data are left blank.

Where to be next: your 3 to 12-month plan

Tell us your months and the places you're considering. We'll send a month-by-month plan with the reason for each move: rain, heat, smoke, typhoons and crowds, from our data.

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Each season's worst two weeks

2023: 5 to 18 March
2024: 1 to 14 April
2025: 19 March to 1 April
2026: 2 to 8 April and 16 to 22 April

How bad, really

Our chart shows timing only. For actual levels we use published ground-station figures:

On 1 February 2024 the Pollution Control Department's Chiang Mai 36t station recorded 15 µg/m³ of PM2.5. On 6 March 2024 it recorded 94, and on 7 March 122 (Chiang Mai University presentation, 3 February 2026).
March and April averaged 2017 to 2023, from IQAir data, were nearly 100 µg/m³ (NASA Earth Observatory, 8 April 2024).

Where to go instead, February to April

For each month, the best-scoring place in each region we track, from our own weather data (score out of 100 for warm, sunny weather; average day high; rain in millimetres per month). Weather only: it does not include crowds, prices or air quality.

February

Ko Lanta, Thailand
Score 100 · day high 30°C · rain 18 mm

Koh Phangan, Thailand
Score 98 · day high 28°C · rain 44 mm

Weligama, Sri Lanka
Score 98 · day high 29°C · rain 61 mm

Bali is not on this list: February and March are its wettest months in our data.

March

Da Nang, Vietnam
Score 97 · day high 27°C · rain 54 mm

Koh Phangan, Thailand
Score 93 · day high 29°C · rain 34 mm

Weligama, Sri Lanka
Score 86 · day high 29°C · rain 77 mm

Bali is not on this list: February and March are its wettest months in our data.

April

Uluwatu (Bali), Indonesia
Score 98 · day high 29°C · rain 139 mm

Da Nang, Vietnam
Score 95 · day high 30°C · rain 72 mm

Koh Samui, Thailand
Score 79 · day high 28°C · rain 103 mm

Uluwatu, on Bali's drier southern tip, gets 139 mm of rain in April in our data, about half of February's 296 mm.

Chiang Mai's better months

From our weather data, November to January is cooler and drier than most of the year: day highs of 29°C in November, 27°C in December and 27°C in January, with 26 mm of rain in January. May is hotter (34°C) with 183 mm of rain, and the smoke chart is low in its last weeks. See Chiang Mai month by month.

About the smoke data

Modelled data. The CAMS global air-quality model (Copernicus Atmosphere Monitoring Service) via Open-Meteo, on a grid about 40 km wide, not ground stations. We use it for timing: which weeks are worse. It reads low on bad days: on the two days we could check against a ground station (6 and 7 March 2024) the station read about 3 times the model. 4 seasons, 2023 to 2026.

Air quality data: CAMS via Open-Meteo, CC BY 4.0. Weekly figures are means of daily PM2.5 for 18.79 N, 98.98 E. Last updated 2026-10-21.

Questions

When is burning season in Chiang Mai?: In our data, smoke builds from late February, and the average of four seasons (2023 to 2026) peaks in the weeks of 12 to 18 March and 2 to 8 April. Each season differs: the worst two weeks were 2023: 5 to 18 March; 2024: 1 to 14 April; 2025: 19 March to 1 April; 2026: 2 to 8 April and 16 to 22 April.
Is all of February to April bad?: No. The chart shows the weeks as a relative index, where each season's worst week is 100. Some weeks sit far below the peak, and the peak week moved between mid-March and mid-April across the four seasons. The index shows timing only, not how high the levels are.
Where do nomads go instead?: For February to April we compare the best-scoring place in each region from our weather data: the Andaman coast, the Gulf islands, Sri Lanka's south coast, Da Nang and, in April, Bali's Uluwatu. See the cards above for each month's score, day high and rainfall.
Which months are better for Chiang Mai?: From our weather data: November to January has day highs of 27°C to 29°C (January 27°C with 26 mm of rain). May is hotter (34°C) and wetter (183 mm of rain in May), and the last weeks of May sit low on the smoke chart. Our weather score does not include air quality, so it rates February and March highly. Use the chart above for smoke timing.
How reliable is this data?: The smoke index comes from a global air-quality model, not from ground stations, and reads low on bad days. We use it for timing, which weeks are worse. For actual levels, see the station figures in "How bad, really" above.