Typical operating window
July–SeptemberSouthern Alps snow normally builds from late autumn, with the commercial window concentrated 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
2.40 m published average · 1.45–4.23 m observed rangeUpper Rakaia electronic weather stationTier B · observed reference · low confidenceSnow character
transitionalCold storm snow can be dry, while foehn wind, rain levels, and sun can change surfaces quickly east of the divide.Public avalanche information
NZAA Canterbury region forecastThe public advisory is recreational. Commercial operators must use their own safety management and hazard assessment.Weather and flight context
Westerly flow creates a strong rain shadow and large differences across the Main Divide.
- Nor’west wind
- Orographic cloud
- Rapid warming and flat light
Meteorological reference area
Methven and Canterbury high country
- Includes
- Canterbury high-country reference sites serving Methven programs.
- Excludes
- Aoraki, Tasman Glacier, Queenstown, and Wānaka 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 reference2.40 m published average · 1.45–4.23 m observed range
- Site
- Upper Rakaia electronic weather station · 1752 m · Distance unavailable — the source summary does not publish station coordinates
- Period
- Thirteen winters; exact years are not listed in the published summary
- Completeness
- Thirteen-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
- The station is a Canterbury alpine reference, not a program-wide snowfall normal.
- Winter snowfall summary from high-elevation stationsEarth Sciences New Zealand · accessed 2026-08-25
Tier CModelled snowfall water equivalent104 mm SWE median · 79–130 mm interquartile range
- Site
- Methven ERA5-Land grid cell · -43.6000, 171.6000 · 5.2 km from Methven 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. The sampled gateway cell can differ substantially from ski elevations. 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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.1 mm SWE | 0 mm SWE | 0.3 mm SWE | 1.4 mm SWE | 4.2 mm SWE | 13.6 mm SWE | 14.8 mm SWE | 17.4 mm SWE | 12.6 mm SWE | 8.3 mm SWE | 4.3 mm SWE | 0.3 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