Weather is probably a major factor when you plan your trip to Yumbo, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually September and August with an average temp of 69°F, while the coldest months are January and December with an average of 68°F. The rainiest months in Yumbo are November, October, March, and December, with each month seeing an average of 18 inches of rainfall.