Island Peak (Imja Tse, 6,189m) is Nepal's most popular trekking peak and the first high-altitude climbing experience for thousands of mountaineers each year. It sits in the heart of the Khumbu, with a base camp at 5,100m and a summit ridge that combines glacier travel, fixed-rope climbing, and a final push to a snow and ice summit with one of the finest views in the Nepal Himalaya.
Getting the timing right for Island Peak requires balancing several factors simultaneously: summit conditions (snow consolidation, wind), the EBC trek itinerary that almost every Island Peak climber combines it with, permit logistics, and the specific weather patterns that characterise the Khumbu's two trekking seasons. This guide breaks down every month.
Quick Overview
6,189m (20,305ft)
October–November (autumn)
April–May (spring)
June–August (monsoon)
Nepal Mountaineering Association (NMA) Peak Climbing Permit
$250 USD per person (autumn), $125 (winter/spring)
5,100m
PD (Peu Difficile — moderate)
70–85% in good conditions
Crampon use, basic fixed-rope technique, glacier travel
Understanding Island Peak's Weather
Island Peak's position in the Chukhung Valley — a side valley east of the main EBC trail — creates a specific microclimate. The valley is more sheltered than the main Khumbu but still subject to the same general weather patterns: jet stream influence in winter, monsoon from the south in summer, and the clear windows of autumn and spring.
Summit temperature range:
- October: -10 to -25°C
- November: -15 to -30°C
- April: -5 to -20°C
- May: 0 to -15°C
Wind at summit: Variable. The jet stream is farther north in autumn (less impact at 6,189m) and moves south in winter (stronger summit winds). Spring sees the jet stream passing north again. Summit wind speeds of 60–100 km/h are possible in November onward and in March.
Month-by-Month Assessment
January and February
Overall rating: Not recommended for most climbers
The Khumbu winter is harsh. Summit temperatures drop to -30°C. Wind speeds are extreme. Most commercial Island Peak expeditions do not operate in these months.
That said: Island Peak has been climbed in January and February by experienced alpinists and small private expeditions. The summit conditions require full winter mountaineering kit — thick insulated boots, heavyweight down suit, and the mental fortitude for extreme cold. Success is possible but the margin for error is narrow.
Logistical note: Some Chukhung Valley teahouses close in December–February. Verify lodge availability before planning a winter attempt.
Trekker numbers: Very few. If you prefer solitude and are experienced with winter conditions, February in particular offers excellent clarity and few other climbers.
March
Overall rating: Fair — improving through the month
March marks the beginning of the spring window. Jet stream influence is decreasing, temperatures are warming, and the fixed ropes installed by early expedition teams begin to appear on the mountain.
Weather: Unstable in early March; improving rapidly through the month. Cloud development begins in the afternoon, especially in the second half of the month. Summit wind is still significant.
Summit success: Lower than peak spring (April) or autumn. Perhaps 50–65% in good conditions.
Advantages: Fewer climbers than April–May, interesting light conditions for photography, the valley is beautiful in early spring with snow still present.
Acclimatization consideration: March climbers must arrive with appropriate acclimatization built up. The acclimatization day activities at Dingboche and Chhukung are essential preparation. The Chhukung Ri (5,550m) acclimatization hike from Dingboche provides excellent preparation at the correct altitude.
April
Overall rating: Excellent — peak spring season
April is the second-best month to climb Island Peak after October. The weather window is generally stable, temperatures are more forgiving than autumn (-5 to -15°C on summit), and the Khumbu is at its most beautiful with rhododendrons blooming in the lower valleys.
Weather: Good overall. Pre-monsoon clouds begin building in afternoon. Morning summit windows are reliable. The rule of "summit before noon" applies in April.
Summit success rate: 75–85% in good conditions.
Crowds: April is the peak spring season for both EBC trekking and Island Peak climbing. Expect 5–15 other climbing teams at base camp and potentially 20–30 people on the summit day. Fixed ropes may have queue waits.
Combination with EBC: April is excellent for the EBC plus Island Peak combination. The standard approach completes EBC first (passing through Namche, Tengboche, Dingboche, Gorak Shep, EBC, and Kala Patthar), then returns to Dingboche for the Chukhung Valley approach to Island Peak.
Permit note: The spring permit ($125 USD) covers March 1–May 31.
May
Overall rating: Good — pre-monsoon challenges increasing
May remains a viable Island Peak climbing window but with increasing pre-monsoon instability.
Early May (1–15): Conditions close to April quality. Afternoon cloud development more pronounced. Still viable for summit attempts.
Late May (16–31): Pre-monsoon weather becomes increasingly unstable. Afternoon thunderstorms can develop rapidly. Summit windows narrow. Only experienced climbers familiar with Himalayan weather patterns should plan late May attempts.
Temperatures: Warmest of any climbing month — summit temperatures may be above -10°C in May. This actually increases avalanche risk on the summit slopes as snow becomes less consolidated.
June, July, August
Overall rating: Not recommended
The monsoon closes Island Peak to all but the most determined or experienced climbers. Heavy snowfall covers the route, crevasse detection becomes extremely difficult, and weather windows are rare and short. Most commercial operators suspend Island Peak expeditions for this period.
Some trekkers visit Chukhung during September as the monsoon breaks — see below.
September
Overall rating: Fair to Good — late monsoon transition
The monsoon withdraws from Nepal progressively through September. High altitude areas like the Chukhung Valley clear earlier than lower elevations.
Early September: Conditions still monsoon-affected. Not recommended.
Late September: The post-monsoon clearing can be dramatic — days of crystal visibility following the final monsoon storms. Island Peak attempts in late September (25th onward) are possible and can be spectacular. The summit snowpack is fresh and consolidated from recent monsoon snowfall.
Risks: Avalanche risk is elevated immediately following heavy snowfall. A period of consolidation (5–7 days minimum of dry weather) should precede any attempt.
October
Overall rating: Outstanding — the prime autumn season
October is the best month to climb Island Peak. Post-monsoon skies are crystal clear, the fresh summit snowpack from the monsoon is consolidated, temperatures are demanding but manageable, and the logistics of the EBC trek timing align perfectly.
Weather: Outstanding. Stable high-pressure dominates the Khumbu through most of October. Mornings are clear and cold; afternoons may see some cloud but the summit is typically clear by the time climbers are descending.
Summit success rate: 80–90% in good conditions.
Temperature at summit: -10 to -20°C. Warm by Island Peak standards. Quality down gloves, a down suit, and good insulated boots are still essential.
Crowds: Peak season. Base camp will have 10–25 teams. A popular summit day (October 10–25) may see 40–60 people on the mountain. The fixed ropes at the crux can create queue waits. Starting your summit push by 1–2 AM (from Camp 1 at 5,600m) is standard to reach the technical section before peak activity.
Combination itinerary: Most commercial guided groups spend 18–22 days total: fly Kathmandu–Lukla, walk to Namche, acclimatize, continue to Dingboche (acclimatize), side trip to Chukhung Ri, continue to EBC and Kala Patthar, return to Chukhung, climb Island Peak (typically 3 days from Chukhung), return to Lukla.
Permit note: The autumn peak-season permit costs $250 USD per person (September–November).
November
Overall rating: Very Good (early) / Challenging (late)
Early November provides excellent conditions comparable to October. As the month progresses, winter settles into the Khumbu.
Early November (1–15): Excellent. Similar to October quality. Fewer climbers than peak October.
Late November (16–30): Conditions deteriorate. Summit temperatures drop to -25 to -30°C. Wind increases. Fixed ropes may be covered by snowfall. Success rates drop to 50–60%.
Advantage of November: The Khumbu is beautiful in November with dusting snow on peaks and very few crowds in the second half of the month.
Permit Information
Island Peak requires a peak climbing permit from the Nepal Mountaineering Association (NMA):
Costs:
- Spring (March–May): $125 USD per person
- Autumn (September–November): $250 USD per person
- Winter (December–February): $125 USD per person
Additional permits required: Sagarmatha National Park entry permit, TIMS card.
Where to obtain: Nepal Mountaineering Association office, Hattisar, Kathmandu. Most commercial operators include permit costs in their package.
Expedition formalities: Island Peak is not restricted (unlike 8,000m peaks) but requires submitting a climbing team roster to the NMA. A licensed Sirdar (lead climbing guide) must be part of the team.