Weather is probably a major factor when you plan your trip to Lago Ranco, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually January and February with an average temp of 56°F, while the coldest months are August and July with an average of 44°F. The rainiest months in Lago Ranco are June, August, July, and May, with each month seeing an average of 16 inches of rainfall.