Weather will likely play an important role when you plan your trip to Monjas, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually April and May with an average temp of 78°F, while the coldest months are January and December with an average of 72°F. The rainiest months in Monjas are June, September, July, and August, with each month seeing an average of 11 inches of rainfall.