Mae Sariang lies in the valley of the Yuam River, which runs through the town from north to south.

While the town itself is at an elevation of 192 metres (630 ft), the land rises much higher just to the east in the Thanon Thong Chai Range, with hills beside the city reaching over 800 metres (2,600 ft).

Temperatures rise until April, which is very hot with the average daily maximum at 37.8 °C (100.0 °F).

The monsoon season runs from May through October, with heavy rain and somewhat cooler temperatures during the day, although nights remain warm.

Mae Sariang is connected to the rest of Thailand by two main roads: Route 108, which enters Mae Sariang from the east (from Chiang Mai) and exits to the north (to Mae Hong Son); and Route 105, which leads south out of the town through Mae Sot to Mueang Tak.