
Motorists had to use fog lights as visibility dropped to about 20 metres.
The fog followed temperatures 12C to 14C late Wednesday night that further dropped to about 5C to 6C in the morning.
Many villagers in the area had to light fires for warmth.
Many tourists stayed in tents in popular areas on Wednesday night, including Doi Pha Mon, Phu Chi Duen, Phu Chi Dao and Phu Chi Fah to wait for the first sunlight and sea of mist in the morning.