Weather - Snow Conditions, Summer and Winter
Aoraki/Mount Cook weather is best described as "variable and vigorous", with considerable precipitation at times. There is marked seasonal variation.
The summer climbing period extends from November to early-April. You must be prepared for a wide range of conditions, from very warm, to cold snowy days. As the summer season advances access on to climbing routes will change.
Summer Temperatures and daylight hours
Actual air temperatures may be 8°C, but can feel like 28°C due to reflected radiation.
- Coolest period: November to mid-December, and March-April. Range -10°C to +10°C
- Warmest period: January & February. Range -5°C to +15°C
- Daylight hours: 05:00 to 21:00, with shorter days later in the season.
Changing Snow Conditions
During November and December access on to routes is usually easier, due to fewer crevasses. Expect fresh snow during storms. Your guide will place greater emphasis on avalanche awareness. Avalanche transceivers are normally carried.
The snowpack is deeper and "wetter". Conditions can be soft underfoot early in the season, especially in the afternoon.
From January onwards the snowpack will consolidate (shallower foot penetration). Crevasses are larger. Crevasse bridging is weakest. Less chance of snowfall. Rock fall hazard increases.
Late Season - March onwards: Conditions are typically "hard" underfoot. Crevassing is at its greatest extent. Night temperatures are dropping. Greater chance of snowfall.
The winter mountaineering period extends from July to mid-October (approximately). During winter daylight hours are shorter, weather is colder, and snow cover is at its maximum extent. Deep snow is common.
Travel on foot is difficult at times, unless aided by skis, snowshoes, or split-snowboards. All AGL parties carry avalanche transceivers. Avalanche awareness and rescue is a focus of winter trips.
- Coolest period (winter): July/August. Range -15°C to 0°C
- Warmest period (spring): September/October. Range -10°C to +5°C
- Daylight hours: 08:00 until 17:00
Winter Period (July/August)
Early winter offers a greater likelihood of powder skiing. Days are short and temperatures coldest – perfect for keeping your powder dry. Less terrain may be accessible due to snow stability/avalanche conditions.
Spring Period (September/October)
It is not uncommon to ski powder after a spring storm, but you are more likely to find corn snow. Corn is better suited to first time backcountry skiers.
Daylight hours are longer and warmer. Snow cover is at its maximum. More terrain can be accessible due to better stability/avalanche conditions.