Weather is probably a major factor when you plan your trip to Manzanillo, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually March and April with an average temp of 81°F, while the coldest months are December and January with an average of 79°F. The rainiest months in Manzanillo are October, September, June, and August, with each month seeing an average of 15 inches of rainfall.