Plan your tramp
Enter your tramp details.
What this solves
A tramp in the Southern Alps is as much about weather as about distance. MetService and the DOC track notes will tell you today what the weather is doing; they will not tell you the probability that a 3-day trip in early March has any usable dry window at all. This tool gives you that probability using NIWA / MetService climate averages from the last decade, broken down by region, altitude and month.
For alpine passes like the Gillespie Pass on the Routeburn, the issue is not whether it rains but whether you get two consecutive dry days at altitude. This tool computes the probability of that.
How to read the result
- Probability is the chance that on any random trip in this month, you experience a usable dry window of N days at altitude.
- Higher altitude lowers the probability — Fiordland at 1,200 m sees twice as many rainy days as at sea level.
- West Coast is the wet side; Northland and Nelson the dry side.
Limitations
- Climate averages, not forecasts. Real-time, you must check MetService 24 h before departure.
- Wind at altitude is not modelled — exposed ridges on the Milford can be impassable in 80+ km/h winds even on clear days.
- Does not capture freak storms; in Fiordland, 200 mm in 24 h happens every few years.
FAQ
Q: When is the driest month in Fiordland?
A: Late Feb to early March has the lowest average rainfall at sea level; at altitude, the difference is smaller.
A: Late Feb to early March has the lowest average rainfall at sea level; at altitude, the difference is smaller.
Q: What about winter alpine?
A: Avoid — Tongariro crossing closes in winter snow; avalanche risk on the Main Divide is high.
A: Avoid — Tongariro crossing closes in winter snow; avalanche risk on the Main Divide is high.
Q: How reliable is the 7-day MetService forecast?
A: Reasonably accurate at sea level; at altitude, the forecast skill drops beyond 48 h.
A: Reasonably accurate at sea level; at altitude, the forecast skill drops beyond 48 h.
Sources
- MetService mountain forecast
- NIWA climate data
- MetService climate summaries for Fiordland, West Coast, and the Southern Alps, 2014–2024