Island Peak is climbed mainly in April to May and October to November. Winter is bitterly cold and windy, and the monsoon brings snow and cloud.
December to February
Extremely cold, with strong winds on the headwall and ridge. Few teams attempt it. Lodges at Chhukung may close, and short days leave little margin on summit day.
March
Cold, with deep snow on the glacier. Early March is difficult; late March improves. Days are clear, and crowds are light.
April and May
The main spring window. Weather is more stable and temperatures are bearable. The glacier is often snow-covered, which helps cover crevasses. Crowds increase in May, so book permits and flights early.
June to September
Monsoon cloud and snow. Not recommended for climbing. Early September can still be cloudy, and conditions improve only late in the month.
Temperatures and wind
At Island Peak Base Camp the temperature drops to minus 10 or below at night in spring and minus 15 in late autumn. On the summit ridge the wind can reach strong levels in the afternoon, so teams start around midnight to be down by noon. A wind-proof outer layer matters as much as warmth.
Choosing a week
Many teams aim for the first half of May or the first half of November. These windows tend to have stable weather and manageable crowds. Avoid arriving at base camp at the same time as a very large group.
October and November
The prime autumn window. Skies are clear and snow is firm. Nights are very cold, and October is busy. Plan acclimatisation carefully. See the best time guide.
Planning around your calendar
Pick the season first, then fit your flights and leave around it. Late March to May and October to mid-November are the usual choices. Avoid booking tight onward flights, since weather can delay a summit.
Crowd levels in the base camp
Popular weeks fill the camps and put several groups on the fixed lines at once. A slightly shoulder-season window can give you a calmer climb with similar conditions.
Why May is busy
May sees many teams on the Imja Tse glacier approach, with warmer weather but heavier traffic. October is clearer and colder. If you want fewer people on the ropes, aim for the early or late days of each window.
