La Nina Japan 2025 Winter
October 2024 forecast update for 2024/25 season in the Nagano resorts and Myoko Kogen
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 this year (which seems to be on the cards ATM) would be the fifth event in just five 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.
Last week we seemed to reach an inversion point where the weather suddenly cools. One day you’re wearing shorts and a t-shirt and then you’re suddenly rugging up at night. The change of season usually occurs around early-mid October, where the stationary boundary forms and moves south, separating the warm summer temperatures from the cooler autumn, along with the return of northerly low pressure & cold fronts that characterise the cooler seasons. However, after a couple of nights of colder temperatures, things started warming up again and it was even a bit muggy. Things can change fast however and the night after I wrote this we saw the first dusting of snow on Mount Myoko, Shiga Kogen and other parts of the Japan Alps. There was more than a dusting up north on Hokkaido though.
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Here’s a recent video looking at the forecast movement of the weather from here through to December
Further reading: Nagano Snow Report and Weather Conditions | Nagano Webcams
More about La Nina Japan 2025 Winter
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 almost certain. The NOAA has claimed on Oct. 10 that, “La Niña is favored to emerge in September-November (60% chance) and is expected to persist through January-March 2025”. 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 cold and winter trend. That’s the good, hopeful news.
FYI Seasonal forecasts can be found on the JMA (Japan Meteorology Agency) site, and here are the latest screenshots for temperatures and then snowfall.
Temperature wise, for central Japan it looks slightly less promising (possibly just below regular) than northern Honshu and Hokkaido (just above regular), but snow fall looks quite promising. However, I want to dig into those disparities a little more.
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 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.
The war on snow in Akakura Onsen.
Observations of recent winters in Nagano during La Niña
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.
Looking at these in total, here are my predictions for the next winter’s weather in Nagano
1. There will be numerous strong cold weather flows into Nagano and western Japan over the season. If you are on the slopes during these times you’ll be having some great powder days.
2. However, as in recent seasons, there will likely be an influx of reasonably intense warmth between these falls. This can bring sunny, warm days quite possibly rain. These days will not be quite as good BUT it should almost definitely have a better base than last season and not be rock hopping.
3. Thanks to the strong cold regular falls, Nagano will have 2-5 metres more snow than last season, as well as a better base. Just that falls could well be irregular, and it may rain occasionally even in the middle of winter.
4. For those heading out into the backcountry, snowfall and conditions are prone to instability with some slab effect after rain. Always check conditions at https://nadare.jp/ first, be careful out there and make sure your insurance is valid. Local guides can be found and bookings made at https://myokokogen.org.
5. Spring is likely to be generally early as La Niña weakens. Many ski areas that have been traditionally open until Golden Week in May (such as Shiga Kogen, Seki Onsen, Akakan, Nozawa Onsen, etc.) may not have enough snow to keep open. It will be heavily dependent on heavy falls and a decent base.
Once again, please understand that this is just an amateur’s personal opinion, not official forecasts and predictions. Fingers crossed that some of my doom scenarios are wrong.
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Note: During the season I write regular snow reports on Myoko/Madarao. You can also find weather and 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
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