September 2026 bulletins favour continued El Niño conditions, but their percentages are not probabilities of powder at a resort. Seasonal temperature and precipitation outlooks do not forecast centimetres of snowfall for individual ski areas.
A map with strong colours can look like a quick answer to where you should book. To use it properly, read four things: who issued it, when it was published, which months it covers and which variable it describes. If one is missing, a headline can imply much more than the forecast actually says.
NOAA: regional context with an issue date
On September 10, 2026, CPC issued a greater than 90% probability of a very strong El Niño event during Northern Hemisphere autumn and winter 2026–27. That figure describes the ocean-atmosphere phenomenon; it does not measure the chance of fresh snow during your vacation.
The September 17 seasonal discussion favours above-normal precipitation in California, with 50–60% probabilities near the coast for December–February, January–March and February–April. It also favours above-normal temperatures in the interior Northwest and much of the northern United States, with 50–60% probabilities in winter windows. These describe regions and multi-month averages, not mountain reports.
NOAA explains that its seasonal outlooks describe temperature and total precipitation and do not estimate seasonal snowfall accumulation. A wet colour over California cannot be converted directly into centimetres for Mammoth. A day-to-day decision needs a recent local forecast.
JMA: what 100% means and how to read terciles
JMA’s September 9 bulletin, covering September 2026 to March 2027, publishes 100% for El Niño continuing through boreal winter. That probability concerns the persistence of El Niño; it is not about snow in Niseko or a particular snowfall intensity.
For its Japan outlooks, JMA uses three categories: below, near and above normal. Thresholds use the 1991–2020 reference period so that each category has a climatological frequency of 33.3%. A higher probability for the upper category changes the distribution of possibilities; it does not state how much a variable will increase.
JMA’s September 24 monthly discussion helps interpret model products and warns that it is not an official forecast for individual countries. For a local decision, consult the relevant meteorological service and the period you actually need.
Andes 2027: the Southern Hemisphere winter needs its own bulletin
The reviewed Chilean Meteorological Directorate index lists its October 2026 seasonal outlook. That material does not verify a snow forecast for Southern Hemisphere winter 2027. Nor does the horizon of JMA’s September bulletin provide grounds for promising snowfall totals that winter.
CPC anticipates weakening El Niño conditions in March–May 2027, with possible neutrality later in the Northern Hemisphere spring. Translating that signal into centimetres at Catedral or Portillo would require additional regional information. This review did not verify an SMN forecast supporting snowfall amounts for Argentina’s 2027 winter.
A useful reading before you book
Save the bulletin with its issue date and valid months. Check whether it describes temperature, precipitation, snowfall or snow depth: these are different variables. As the trip approaches, replace seasonal context with local forecasts and consult operating reports. A climate signal helps explain scenarios, but it does not reserve a storm for your week.
Frequently asked questions
Does a 60% chance of above-normal precipitation mean 60% more snow?
No. It is a probability of falling within a category, not a percentage increase in snow.
Does a warmer winter rule out all snowfall?
The outlook describes the seasonal average. It does not determine every event or replace the local forecast for your travel dates.
Sources and editorial approach
This guide draws on the linked sources. We distinguish historical facts, announced dates and conditions that need a current check. Confirm operations, access and services with the destination operator before booking.
- NOAA/CPC: ENSO diagnostic, September 10, 2026
- NOAA/CPC: seasonal discussion, September 17, 2026
- NOAA: what seasonal outlooks measure
- JMA: ENSO outlook, September 9, 2026
- JMA: categories and climate reference
- JMA: model discussion, September 24, 2026
- Chilean Meteorological Directorate: outlook index