Planning for the weather is a good way to make your trip to Poso relaxing and enjoyable, especially when you're splurging. The hottest months are usually October and September with an average temp of 77°F, while the coldest months are September and January with an average of 77°F. The rainiest months in Poso are April, March, May, and November, with each month seeing an average of 16 inches of rainfall.