If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Tomah: The hottest months are usually July and August, with an average temperature of 20°C, while the coldest months are January and February, with an average of -5°C. The snowiest months in Tomah are January, April, March and February, with each month seeing an average of 24 cm of snowfall.