Typical operating window
July–OctoberSouthern Alps storms begin building winter cover from late autumn; useful glacier skiing normally develops in winter.Verified planning context
Snow, weather and avalanche context
Historical patterns help you compare trips. They do not predict your week or replace the operator's daily decisions.
Strongest comparable snow evidence
3.95 m published average · 2.58–5.32 m observed rangeMueller Hut electronic weather stationTier B · observed reference · low confidenceSnow character
maritimeStorm snow can be dense near the divide. Cold clear periods preserve dry snow, while spring sun drives fast surface change.Public avalanche information
NZAA Aoraki/Mount Cook regionNZAA states that its public forecast is not for commercial operators. The heli-ski operator must maintain its own assessment.Weather and flight context
Strong westerlies produce large precipitation gradients across the Main Divide.
- Main Divide cloud cap
- Severe alpine wind
- Glacier flat light and rapid warming
Meteorological reference area
Tasman Glacier and Aoraki high-alpine context
- Includes
- Tasman Glacier and nearby Aoraki high-alpine reference sites.
- Excludes
- Queenstown, Wānaka, and Canterbury profiles.
- Elevation
- No verified operator-terrain elevation band is public. Each evidence value retains its site elevation.
Evidence pack
Measurements, claims and gaps stay separate.
Tier BObserved winter snowfall reference3.95 m published average · 2.58–5.32 m observed range
- Site
- Mueller Hut electronic weather station · 1818 m · Distance unavailable — the source summary does not publish station coordinates
- Period
- Ten winters; exact years are not listed in the published summary
- Completeness
- Ten-year summary; annual values and missing periods are not published on the source page.
- Method
- Earth Sciences New Zealand published mean and observed minimum-to-maximum winter snowfall.
- Limitation
- A short single-point series cannot represent glacier accumulation or every heli-ski elevation.
- Winter snowfall summary from high-elevation stationsEarth Sciences New Zealand · accessed 2026-08-25
Tier CModelled snowfall water equivalent729 mm SWE median · 656–831 mm interquartile range
- Site
- Tasman Glacier ERA5-Land grid cell · -43.6000, 170.2000 · 1.4 km from Tasman Glacier reference point
- Period
- Calendar years 1991–2020
- Completeness
- 360 monthly means; all 30 calendar years contain 12 values.
- Method
- ERA5-Land monthly mean daily snowfall accumulation was multiplied by calendar days and 1,000, then summed by calendar year.
- Limitation
- This reference area supports evidence discovery and comparison. It is not an operating-area or tenure boundary. This unadjusted 0.1° reanalysis grid cell is not an observation, snow depth, or terrain-wide total. Grid elevation and wind redistribution can cause substantial local bias.
- ERA5-Land monthly averaged data from 1950 to presentCopernicus Climate Change Service · accessed 2026-08-26
Monthly evidence
Each cell keeps its measurement type and unit. Reanalysis water equivalent is not snow depth. Text-only cells preserve a representative data gap.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2.6 mm SWE | 2.3 mm SWE | 5.4 mm SWE | 18 mm SWE | 54 mm SWE | 95.8 mm SWE | 121.9 mm SWE | 99.8 mm SWE | 99.6 mm SWE | 81 mm SWE | 48.8 mm SWE | 14.9 mm SWE |
Commercial operator assessment
Operator assessment process not independently verifiedThe operator must assess current snow, avalanche terrain, weather, aircraft limits, and rescue options. No private operational plan is inferred.
Sources and evidence notes
- WMO Climatological NormalsWorld Meteorological Organization · accessed 2026-08-25
- ERA5-Land hourly data from 1950 to presentCopernicus Climate Change Service · accessed 2026-08-25
- New Zealand Avalanche AdvisoryNew Zealand Mountain Safety Council · accessed 2026-08-25
- Published operator and trip inventoryHeliski International editorial team · accessed 2026-08-25
- Winter snowfall summary from high-elevation stationsEarth Sciences New Zealand · accessed 2026-08-25
- ERA5-Land monthly averaged data from 1950 to presentCopernicus Climate Change Service · accessed 2026-08-26
- What is the New Zealand Avalanche Advisory?New Zealand Mountain Safety Council · accessed 2026-08-25