Mid September through April. Camping La Junta also opens and closes around these dates. Outside the season tends to be humid, cold and too rainy, main river crossings closed, and generally not recommended to go.
Hiking & trail conditions:
Septiembre hasta fines de abril. Almost all the beauties of the valley that can be accessed through established trails can be visited and enjoyed throughout the season. You should avoid winter. In spring, with the abundance of water, the waterfalls fall in all their splendor. Snow-capped hills and rocky access must wait until the longer and warmer days clear and dry out the terrain. In January and February, on days without rain, all trails are open. In March the days begin to shorten, it cools down and the beautiful ulmo flowers paint the landscape in a valley that once again belongs to the forest and its inhabitants due to the decrease in the number of visitors. In April, the lengas are revealed high up with their intense red, the mushrooms shine in the forest on sunny days and the hills without snow begin to wait for the new cycle.
Best time to climb:
From December through March. Depending on the amount of winter's snow fall, melting snow can streak down walls and their cracks until late November to mid December. North facing walls, like Trinidad, dry the quickest. December can be the best climbing month if the conditions are right. The days are at their longest (15 hours of light) allowing more time to complete long routes in one push. Tabano flies have not yet come out. December tends, however, to be rainier than January or February. January and especially February is generally the dryest yet also the busiest. March can also be great, but the days become noticably shorter. April days are even shorter, cooler and generally rainier.
Best for peace & quiet,
Best for saving $:
Avoid going in Jaunary & February if you're planning and basing your trip on a budget or looking for escaping the beaten tourist path. These months are the busiest thus the high-season prices. Accommodations and public transportation can be full throughout the South due to swarms of vacationing Chileans. Cochamó's peaceful nature can at times be lost among-st the multitudes.
Months to avoid:
May to mid September. Although there are the occasional sunny days, much of the days sun is lost behind the northern mountains. The days are very short. The Refugio Cochamó and Camping La Junta, furthermore, are closed. Many river crossing are removed making moving around the valley difficult or impassable. Plus it's rainier, muddy, more humid and cold.