Authorities have warned that this year's haze crisis in Chiang Mai is among the most severe in recent years, with pollution-related illnesses more than doubling. More than 1.6 million vulnerable people across 11 provinces have been affected.

Thick haze continued to blanket Chiang Mai yesterday, as PM2.5 levels remained several times above safe limits. Hourly air-quality data from Chiang Mai University's CCDC monitoring system showed extreme readings, including a peak of 808 microgrammes per cubic metre in Chiang Dao district -- more than 20 times the recommended safety level. 

The city ranked second globally for air pollution, according to IQAir.

Hospitals have reported a sharp rise in patients suffering from pollution-related illnesses.

A specialist at Lanna Hospital said outpatient numbers had more than doubled from normal levels.

Common symptoms include allergic skin rashes, asthma flare-ups, unexplained shortness of breath, severe nasal inflammation, frequent nosebleeds and eye irritation.

The doctor urged residents to wear N95 masks outdoors, keep doors and windows closed, and use air purifiers indoors where possible.

Red-level pollution has affected 11 provinces: Chiang Mai, Chiang Rai, Mae Hong Son, Nan, Phayao, Lampang, Lamphun, Phrae, Bueng Kan, Nakhon Phanom and Nong Khai. More than 1.6 million vulnerable people face health risks.