What Is the Temperature at the Summit of Mount Everest?

Air temperature at the summit of Mount Everest averages roughly −26°C (about −15°F) during the spring climbing season and plunges to around −36°C (−33°F) in midwinter, though these numbers only tell part of the story. Persistent high winds drive wind chill values far lower, and the summit sits near the boundary of the jet stream, where conditions can shift from survivable to deadly within hours. Understanding what “temperature” really means at 8,849 meters requires looking well beyond what a thermometer reads.

Average Temperatures by Season

Everest’s summit does not hover at one fixed temperature. The climbing season, which peaks in May, offers the mildest window, though “mild” is relative. Research comparing summit conditions on Everest and K2 found an average air temperature of about −26°C during the climbing season on Everest, with winds averaging around 16 meters per second (roughly 36 mph).¹ In midwinter, the same study measured an average of about −36°C, accompanied by winds that more than doubled to around 41 meters per second (over 90 mph).¹

The pre-monsoon and post-monsoon periods sit between those extremes but bring significant variability. Large-scale weather systems passing through can swing the temperature by many degrees in a single day. Studies of conditions at the South Col, about 900 meters below the summit, show that even during the “favorable” pre-monsoon window, cold spells can briefly push conditions close to winter levels.²

This is why expeditions cluster their summit attempts into a few days each May. They are not just waiting for warmer air; they are waiting for a brief alignment of tolerable temperature, reduced wind, and a temporary retreat of the jet stream. Even so, climbers routinely face air temperatures that would be dangerous anywhere on Earth’s surface, let alone at an altitude where each breath delivers barely a third of the oxygen found at sea level.

Why Wind Chill Is the Number That Matters

Raw air temperature on Everest is cold enough to be dangerous, but it is the wind chill temperature (WCT) that determines whether a climber’s exposed skin freezes. Wind strips body heat far faster than still air does, and the summit is almost never still. Research focused specifically on freezing risk found that during the spring climbing season, WCTs of around −50°C and flesh-freezing times of about 5 minutes are typical near the summit.³ During severe storms, those values approach −60°C and the time for exposed skin to freeze drops to roughly one minute, conditions normally seen only in midwinter.³

South Col data from environmental monitoring paints a similar picture, with WCTs dipping to −50°C and flesh-freezing times as short as 2 minutes during the pre- and post-monsoon periods.² Year-round, the typical WCT near the summit stays below −30°C, and the flesh-freezing time is always less than 20 minutes, even on the calmest days.³ There is essentially no point in the year when frostbite is not a real threat at the summit.

This gap between air temperature and wind chill is why summit-day fatalities and frostbite injuries can occur even when weather forecasts look “acceptable.” A climber checking a forecast that says −25°C may feel reassured, not realizing that 50-mph gusts transform that number into something vastly more dangerous for any patch of skin exposed for more than a few minutes.

The Jet Stream and Its Grip on the Summit

Everest’s summit altitude places it right at the lower edge of the subtropical jet stream for much of the year. This river of fast-moving air, flowing west to east across the Himalayas at speeds that can exceed 150 mph, is the single largest driver of the extreme wind and cold conditions at the top. During winter and early spring, the East Asian jet stream frequently sits directly over the summit, creating the ferocious winds and bitter wind chills described above.

One visible consequence of this jet-stream interaction is the famous snow plume that streams from Everest’s peak. Research using meteorological datasets has shown that the plume forms when high winds from the East Asian jet stream combine with fresh snow deposited by earlier storms, blowing it off the summit in a long horizontal banner.⁴ If you can see the plume from base camp or from a satellite image, it is a clear signal that winds near the top are far too strong for climbing.

In late May, the jet stream typically migrates northward as the Asian monsoon approaches, creating the brief window when summit winds drop enough for attempts. That window is narrow, sometimes just a week or two, and its timing varies year to year. If the jet stream retreats late or returns early, the climbing season can shrink dramatically. This pattern also explains why successful winter ascents of Everest are exceptionally rare: the jet stream sits stubbornly over the summit for months, bringing continuous winds that make wind chill values approach −70°C or lower.

How Everest Compares to K2

K2, the world’s second-highest peak at 8,611 meters, is often called the more dangerous mountain, but the temperature comparison between the two summits depends on the season. During the climbing season, Everest’s summit runs colder than K2’s by a meaningful margin. Research comparing the two found average climbing-season temperatures of about −26°C on Everest versus −21°C on K2, with wind chill temperatures of roughly −45°C versus −37°C and flesh-freezing times of about 6 minutes on Everest versus 11 on K2.¹

In midwinter the relationship flips. K2’s average winter temperature was measured at about −45°C, nine degrees colder than Everest’s −36°C. K2’s winter wind chill of roughly −76°C was also harsher than Everest’s −66°C, though both values are extreme enough to freeze exposed skin almost instantly.¹ The reversal stems largely from K2’s location and geometry: it sits farther north and in a region where winter high-pressure systems bring extraordinarily cold, dense air masses, while Everest’s winter severity comes more from relentless wind than from rock-bottom air temperatures.

This comparison underscores that raw altitude alone does not determine how cold a summit gets. Latitude, regional weather patterns, and proximity to specific jet-stream tracks all shape the thermal environment in ways that make two mountains of similar height feel quite different.

Solar Radiation and Unexpected Warmth

Not everything about temperature at the summit is intuitively cold. At extreme altitude, solar radiation intensity increases because there is less atmosphere to filter it. Research on heat balance during Everest climbs has noted that global solar radiation climbs with elevation due to reduced atmospheric mass overhead, and that snow and ice on the upper south-facing slopes reflect additional solar energy onto climbers and surfaces.⁵

On a calm, clear day, a climber in the sun can feel surprisingly warm even while the air temperature reads well below zero. The high UV index at altitude, amplified by reflection off snow, can cause rapid sunburn on exposed skin while frostbite threatens simultaneously on any shaded or wind-exposed surface. This paradox creates localized microclimates: a sheltered sunny spot on the South Col might feel tolerable while a shadowed, wind-blasted ridge a hundred meters away is lethal.

This solar effect also has implications beyond human comfort. Weather stations installed on Everest have documented that surface energy fluxes at the South Col and even potentially at the summit are sufficient to cause melting of snow and ice despite air temperatures that never rise above freezing.⁶ In other words, the sun can warm ice surfaces above the melting point even when the air surrounding them is below zero, a reality that has consequences for glacier stability in the region.

Measuring Temperature Where Equipment Breaks

Getting reliable temperature readings at Everest’s summit is harder than it sounds. For decades, summit conditions were estimated using data from lower weather stations, atmospheric models, and occasional readings from handheld instruments carried by climbers. That changed with the installation of automated weather stations, including the two highest on Earth at 8,430 meters and 7,945 meters, as part of a 2019 expedition.⁶

These stations have transformed our understanding of summit-region weather, but they come with real limitations. Recovery of equipment that had been destroyed by the environment revealed that wind speed sensors suffer from mechanical breakage and the growth of rime ice, both of which produce incorrect measurements that are not always obvious from the data alone.⁷ If wind speeds are recorded incorrectly, wind chill calculations derived from them are also wrong. Temperature sensors face their own challenges: rime ice can insulate them from the air, and intense solar radiation can heat the sensor housing above the true air temperature, especially if the ventilation fans fail.

The result is that even with the world’s highest weather stations in place, summit temperature data requires careful quality control. Researchers compare station readings against atmospheric reanalysis models and cross-check one sensor’s record against others to flag anomalies. The data is far better than what existed even five years ago, but anyone citing a precise summit temperature should know it comes with meaningful measurement uncertainty.

Climate Change and the Highest Glacier

One of the most striking findings from recent monitoring is that Everest’s high-altitude environment is not static. The South Col Glacier, sitting at about 8,020 meters, is losing mass at an accelerating rate. Ice core and weather station data show that contemporary thinning rates approach roughly 2 meters of water equivalent per year, meaning several decades’ worth of snow accumulation can be lost in a single year now that bare glacier ice is exposed.⁸

This loss is driven not primarily by warmer air temperatures, which remain persistently below freezing, but by the surface energy balance discussed earlier: solar radiation, sublimation (ice turning directly to vapor in the dry, thin air), and wind erosion. The weather station observations suggesting that melt can occur at the South Col and possibly at the summit itself were a surprise to many researchers, prompting a rethinking of how glacier models handle melt at extreme altitude.⁶ Traditional models that relied solely on air temperature to predict ice loss were missing processes that matter enormously at high elevation.

Whether the summit temperature itself has been warming over time is harder to say with confidence, because continuous high-quality records only go back a few years. Atmospheric reanalysis datasets suggest modest warming trends across the Himalayan region at high altitude, consistent with the broader pattern of amplified warming at elevation seen in mountain ranges worldwide. But the scale of that warming at the specific elevation of Everest’s summit remains an area of active research, and the short observational record makes it premature to assign a firm per-decade warming rate.

What Forecasts Miss and Climbers Get Wrong

Climbers today have access to detailed weather forecasts for the summit, typically derived from global atmospheric models with resolution fine enough to give hour-by-hour predictions. These forecasts have improved dramatically and are credited with helping teams choose safer summit windows. But several common misunderstandings persist about what those forecasts mean.

The most common mistake is treating the forecast air temperature as the temperature you will experience. As the wind chill data makes clear, the “feels like” temperature at the summit is routinely 20 to 30 degrees colder than the air temperature. A forecast of −25°C with 40-mph winds means a wind chill below −50°C. The difference between those two numbers is the difference between a challenging but manageable cold exposure and exposed skin freezing in minutes.

Another overlooked factor is how quickly conditions can change. The passage of a single weather system can shift summit temperatures by 10°C and increase wind speeds by a factor of three in a matter of hours. Climbers high on the mountain often cannot descend fast enough to escape a storm that arrives ahead of forecast, which is why some of the worst disasters on Everest have involved groups caught by weather that deteriorated faster than predicted. The 1996 tragedy is the most famous example, but similar scenarios have played out many times since.

Solar radiation adds another layer of complexity that forecasts typically ignore. Two climbers at the same altitude on the same day can have wildly different thermal experiences depending on whether they are on a south-facing sunlit slope or a north-facing shaded ridge. The energy input from the sun at that altitude is intense enough to make a 20-degree difference in the effective surface temperature of a climber’s gear. Forecasts give a single air temperature for a grid cell, not a microclimate map.

Finally, the extreme altitude itself changes how the body handles cold. With less oxygen available, the body’s metabolic heat production drops, and the cardiovascular system is under strain, reducing blood flow to extremities. This means a given air temperature is physiologically more dangerous at 8,800 meters than the same temperature would be at sea level. Two people standing in −25°C air would face very different frostbite risks depending on whether they were at a cold-weather bus stop or on the summit of Everest, even if the wind were identical.