Planning for the weather is an important factor for making your trip to Des Moines a success, especially when you're splurging. The hottest months are usually July and August, with an average temperature of 24°C, while the coldest months are January and December, with an average of 4°C. The snowiest months in Des Moines are December, March, January and February, with each month seeing an average of 18 cm of snowfall.