According to the United States Census Bureau, the township has a total area of 36.2 square miles (93.6 km2), all land.

The main geographic feature of Summit Lake Township is the Buffalo Ridge, a drainage divide between the Mississippi and Missouri River systems.

Summit Lake once existed in section 11 of the township, but was drained in subsequent years.

If the lake existed today, it would have the highest elevation of any body of water within the state of Minnesota.

Summit Lake, the namesake of the township, no longer exists having been drained and lost in the passing years.

Summit Lake Township is located in Minnesota's 1st congressional district, represented by Mankato educator Tim Walz, a Democrat.

Summit Lake Township is represented by Nobles County Commissioner Marvin Zylstra