Weather is probably a major factor when you plan your trip to Santander, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually May and June with an average temp of 82°F, while the coldest months are February and January with an average of 80°F. The rainiest months in Santander are July, September, October, and August, with each month seeing an average of 15 inches of rainfall.