Taking the local weather in Idaho Falls into account is an important factor for planning your visit, especially if you plan to spend your trip by the pool. The hottest months are usually July and August, with an average temperature of 20°C, while the coldest months are January and December, with an average of -4°C. The snowiest months in Idaho Falls are March, January, February and December, with each month seeing an average of 20 cm of snowfall.