Planning for the weather is a good way to make your trip to Puerto Montt relaxing and enjoyable, especially when you're splurging. The hottest months are usually January and February with an average temp of 57°F, while the coldest months are July and August with an average of 46°F. The rainiest months in Puerto Montt are August, June, July, and May, with each month seeing an average of 13 inches of rainfall.