Doi Inthanon National Park reported that the temperature atop the mountain in Jom Thong district measured 10C in the morning.
The park said many tourists went up the mountain to the Kiew Mae Parn Viewpoint to see the rising sun. They were not disappointed, thanks to a clear sky.
Meanwhile, the temperature at the park office measured 12C.
In Loei, police deputy commander Pol Colonel Yutthana Chokechai said several major roads, including Loei-Phu Rua, Loei-Phu Kradueng and Loei-Chiang Khan, were enveloped in thick fog in the morning.
The Loei weather office reported that the temperature in the northern province dropped 1-2 degrees Celsius at several spots.
The office said the Phu Luang Wildlife Sanctuary saw a temperature drop to 11C, while the mercury at Phu Kradueng National Park, Phu Rua National Park and Loei Highland Agricultural Research and Development Centre in Phu Rua district measured 13C.