La Nina Japan 2025/26 Winter

First, a little bit of explanation of how we come to the following conclusions. We rely on a variety of sources – both formal (JMA, NOAA and other weather bodies) and informal (resort locals and knowledgeable pundits like those on ski.com.au), as well as my personal experience of the region over 30 years. Working with all these there tends to be a diversity of opinion but we do our best to collate it all into something intelligible.

Secondly, as much as we might not like (or many try to deny it), the effects of climate change are becoming clearer. And that means that traditional weather models are not as reliable anymore. Another La Niña seems to be a possibility according to most pundits this year, albeit likely a very weak one. If it was to happen it would be the fifth or sixth event in just six years (see below) — well above the average of one every four years, and a frequency only previously seen twice since 1900. So there’s a bit of presumption and guesswork based on the last 3-5 seasons.

Lastly, this is our personal perspective on this winter weather, based on the above and could be completely wrong! So please take it as general advice only and don’t do all your bookings based upon it.

Further reading: Nagano Snow Report and Weather Conditions | Nagano Webcams

Nagano Season Forecast: More about La Nina Japan 2025/26 Winter

ENSO / La Niña chance: Seasonal outlooks currently favour a transition from neutral toward a short-lived La Niña in late-2025 / early-2026, though probabilities drop for the core winter months and uncertainty remains. This is the single biggest driver of seasonal signal uncertainty for Japan.

Otherwise, looking first at the El Niño/La Niña phenomenon that has a major impact on winter weather, not in Japan but across the globe. Both the US weather authorities and the Japan weather agency have announced that the La Niña phenomenon is likely, but not strong. The NOAA has claimed that, “A transition from ENSO-neutral to La Niña is likely in the next couple of months, with a 71% chance of La Niña during October – December 2025. Thereafter, La Niña is favored but chances decrease to 54% in December 2025 – February 2026“. Next is the dipole mode phenomenon in the Indian Ocean, but this winter, you can see the trend of negative dipole phenomenon. A positive dipole is a warm winter factor. Based on all of these, this winter, the westerly winds are likely to snake from northwest to southeast near Japan, and the cold weather in Siberia is likely to flow into Japan, which means a fairly usual cold and winter trend. That’s the first bit of hopeful news.

FYI Seasonal forecasts can be found on the JMA (Japan Meteorology Agency) site, and here is the latest screenshot for predicted snowfall.

Temperature wise, for central Japan it looks fairly bog standard with predicted near-normal temperature occurrence.

Let’s look at the trend for Japan in recent years:
20-21 & 23-24 El Niño / Positive dipole mode → Warm winter with under-average and uneven falls
21-22-23-25 La Niña / Negative dipole mode → Cold temperatures and heavy, even record snowfalls.

However, when looking at the average temperature distribution near Japan in January during these seasons, during El Niño it’s blustery, but also during La Niña it’s slightly higher than average. So forecasting ‘average temperatures’ is seemingly a positive.

The war on snow in Akakura Onsen.

Observations of recent winters in Nagano during La Niña Japan

Under the old weather models westerly winds usually brought cold weather and heavy snow falls to the region but, more recently, sometimes there was unseasonably warm periods in-between heavy falls and sometimes heavy rain. This is because the high pressure systems pushing cold winds from the north around Siberia and causing a lake sea effect as it crosses the Japan Sea have actually been declining in recent years. After the nor-westerly winds bring cold fronts into Japan, it is now taking longer to accumulate strength for the next cold front. This therefore causes an influx of warmer weather during the cold front accumulation period, thereby oft bringing unseasonably warmth and heavy rain.

Additionally, average global temperatures in January are rising year after year, especially in the last few years. With this warming, the cold weather in Siberia is becoming more difficult to build up, plus the cold weather buildup period is getting longer. Sadly this is a trend that seems to continue and quite likely worsen.

Nagano Season Forecast: What about specific resort forecasts?

Here’s how I estimate the Nagano Season Forecast chances of above-average snowfall (or “good snow year”) for some major resorts in Nagano, based on current info + historical patterns. Also some caveats (risks) for each.

Nagano Season Forecast: Overall Interpretation

• The consensus of current forecasts is neutral to weak La Niña Japan rather than a strong snow-boosting La Niña Japan. That pushes the expectation toward a season with variable snow: some excellent dumps, but also more frequent “holes” (warm spells, lower snow depth) than in very strong La Niña years.

• Historical data suggests that even in La Niña Japan years Nagano City (and by proxy some resorts) have more often been below average than above average. E.g. between 1954-2014 there were 13 La Niña cycles: in only ~5 did snow exceed the long-term average.

• Resorts with high elevation and favorable terrain (steep aspect, good access to moisture) are more likely to come out “on top” if things go well. Lower elevation and more sheltered/valley base areas are riskier.

La Niña Japan, La Nina Japan, Nagano season forecast

Disclaimer

This is a resort-by-resort summary of the probabilities & risks for the 2025-26 Nagano ski season, has been calculated by using available ensemble forecasts, climatological data, and historical La Niña / ENSO-neutral behaviour. Because detailed model ensembles by individual resort are not yet widely published, these are estimates (+/−) rather than firm probabilities.

Short, practical advice for planning

• If you want more reliable powder days, favor higher-altitude Nagano resorts (Hakuba, Shiga Kogen, Nozawa Onsen) for bookings.

• For flexible trips, pick accommodation with free-change or easy transit — lower-base resorts may be more subject to warm spells.

• Keep an eye on updated ENSO bulletins from NOAA/CPC and JMA from October → December; seasonal signals typically sharpen in autumn.

Help us out!

Note: During the season I write regular snow reports on Myoko/Madarao. You can also find weather and Nagano season forecasts for the following Nagano ski resorts – Hakuba, Nozawa, Shiga Kogen. If you like my work please do consider donating a little something here to keep this nonsense going. You can also book your ski shuttles here, private transfers here, or your accommodation as below

Book now to get the best La Niña Japan deals!

• Myoko Kogen
• Nozawa Onsen
• Hakuba
• Shiga Kogen & Snow Monkeys
• Madarao Kogen
• Togari Onsen
• Nagano City

Can’t find what you want? Send us a accommodation request or ask a question.

La Niña Japan, La Nina Japan, Nagano season forecast