(Image: Volcano Villarica in the evening)
An English language guide to some Volcano and Mountain ascents in the Los Lagos, Los Rios & La Araucanía regions of Chile - Basically between Puerto Montt and Los Angeles, Chile. These are ascents that I have personally done over the last few years.
December to February are the best months with January and February being the busiest in terms of general tourism. Snow will still be present on higher ground early in the season and can extend until the end January. The busiest trekking months are January and February but depending on the weather, March can still be a good time to go.
You can see up to date information on the volcanic activity of volcanoes in Chile on this page: http://www.sernageomin.cl/red-nacional-de-vigilancia-volcanica/ (in Spanish).