Quick Answer
November to March is trekking season. December-February is warmest (8-18°C) with the longest days. But March (autumn) offers golden lenga forests, fewer crowds, and calmer winds — it's the local secret.
Peak Season (December–February)
Summer in Patagonia brings the longest days (17+ hours of light) and the warmest temperatures. Torres del Paine W Trek refugios sell out by August for this window. El Chaltén is buzzing with trekkers. Expect wind — always — but storms are shorter. This is when everything is open and accessible. Book flights (Buenos Aires/Santiago to El Calafate or Punta Arenas) months ahead.
Shoulder Season: March (Autumn)
March is increasingly popular among repeat visitors. The lenga beech trees turn gold and red, creating dramatic colour against granite peaks. Crowds thin dramatically after mid-March. Refugios offer last-minute availability. Wind tends to be calmer. The risk: days are shorter, and some facilities start closing late March. But the photography opportunities are unmatched.
Shoulder Season: October–November (Spring)
Spring brings wildflowers and melting ice, but many trails are still snowy and some refugios don't open until November. Weather is highly unpredictable — four seasons in one hour is real. Lower prices and zero crowds if you're prepared for variable conditions.
Winter (April–September): Mostly Closed
Most trekking infrastructure closes. Torres del Paine remains open but with limited services and winter conditions (snow, ice, short days). Perito Moreno Glacier is accessible year-round from El Calafate. Ushuaia becomes a ski destination. This is not the time for the classic treks unless you're experienced in winter mountaineering.
Argentina vs Chile Side
El Chaltén (Argentina) is the trekking capital — free day hikes to Fitz Roy with no permits needed. Torres del Paine (Chile) requires park entry fees ($35) and W Trek refugio bookings. Both sides are incredible. A common route: fly into El Calafate → El Chaltén (3 days) → Perito Moreno Glacier (1 day) → bus to Torres del Paine (3-5 days) → fly out of Punta Arenas.