Taking the local weather in Boise 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 August and July, with an average temperature of 16°C, while the coldest months are December and February, with an average of 3°C. The rainiest months in Boise are January, November, December and October, with each month seeing an average of 237 mm of rainfall.