Weather is probably a major factor when you plan your trip to Samosir, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually June and July with an average temp of 76°F, while the coldest months are January and February with an average of 74°F. The rainiest months in Samosir are November, December, October, and September, with each month seeing an average of 17 inches of rainfall.