Tourists flocked to a mountain to enjoy cool weather as temperatures dropped in northern Thailand.

Locals hiked up the Doi Inthanon National Park, where the mercury plummeted to a low of 5 degrees Celsius, as a cold wave swept over Chiang Mai province on December 19.

Chiang Mai saw temperatures as low as 18 to 19 degrees Celsius, with frost blanketing the grass at the Doi Inthanon National Park.

The Thai Meteorological Department (TMD) said a strong high-pressure system was prevailing over northern Thailand and causing cold temperatures.

A further drop of 4 to 6 degrees Celsius in the north was forecast from December 20 to 25 as another cold front from China was expected to blow in.

Meanwhile, the capital Bangkok and its vicinity was predicted to experience temperature drops of 3 to 5 degrees Celsius.

The TMD said the period is expected to be the coldest so far during the holiday season in Thailand.