The Hiker's Guide to Weather in Daisetsuzan National Park

“What will the weather be like when I’m hiking?” is one of the most common questions we get from our guests. It’s also the first thing I think about when I wake up when guiding a hiking tour and the last thing I check before going to bed. Needless to say, the weather plays a massive part in any hiking adventure in the Daisetsuzan National Park - no surprise given the exposed nature of the Daisetsuzan’s ridges and plateaus.

Despite the relatively low elevation – even Mt. Asahidake the highest peak tops out at just 2293m - the Daisetsuzan gets the full brunt of Hokkaido's varied weather. On top of that, once you get over ~1500m you are above the treeline and exposed to the full brunt of the weather.

Hokkaido experiences quite a lot of seasonal variation in the weather and the Daisetsuzan experience almost any kind of weather you can think of – from sweltering sunny days, to intense thunderstorms and metres of snowfall. The snowfall is the most significant part of the climate here - the mountains are named "Big snow mountains" after all.

The park has a unique environment and with a close eye on the weather and proper preparation, it is possible to safely and comfortably experience it for yourself. In this post, I will break down the weather by season, including monthly averages, to help you plan your hiking trip in the Daisetsuzan National Park.

Please keep in mind that these figures are just monthly averages. While they give you a guide of what the weather is usually like, we all know the weather can be unusual. It goes without saying that you should defer to an accurate weather forecast on the day. Read on to find out more about each season.

In town the snow has melted by April and cherry blossoms bring colour to local parks. However, as the photo and temperatures above show, spring is winter by a different name up in the mountains. While the snow stops falling by late April, it still covers much of the landscape through May, making skiing a much easier way to get around.

Keen local hikers do start getting out during spring, but a decent pair of stiff-soled alpine boots are essential and you’ll need to pack crampons and an axe for when you encounter hard patches of frozen snow.

Another challenge posed by the snow is many roads to the trailheads don’t get ploughed during winter, meaning they are still impassable until June.

Snow way!

Spring kicks off the big transition from a uniform carpet of white to a varied landscape of greens, reds and oranges. Exposed ridgelines melt first, while deep gullies that were filled with snow over winter stay buried long into summer. This process accents the mountains with changing patterns that are visible even from space.

It’s impressive to watch the snow melt away, but keep an eye on the date. As you can see, patches of white linger through summer all the way until September, despite the weather feeling much more like summer.

While town temperatures soar above 30°C in summer, the Daisetsuzan peaks provide an escape from the heat. Hiking season is here in full force. Yet, there is a lot of variation to prepare for.

Cloudy days are the norm and they can feel cool, with the wind biting even if the temperature isn’t low. A wind-breaking jacket and trousers make a huge difference, and a warm layer in your pack is essential for stops or emergencies.

With all this talk about snow and cold, it's easy to forget it gets hot here too. However, the calm sunny days will feel hot and the sun packs a punch. It’s important to be able to cover your skin if you’re getting cooked, so light long sleeves, trousers and a hat are the way to go. Also be sure to carry plenty of water.

While rain is less common in summer, the rainfall we do get is often heavy, as clouds that form over the hot, low-lying areas drop their moisture in one go as they hit the mountains. So, having a set of waterproofs tucked into your pack is a life saver.

My summer go-to starts with a quick-drying, loose base layer, often my only upper layer when moving. I wear quick-drying lightweight trousers to avoid sunburnt legs and a cap with sunscreen on my neck.

I carry a lightweight fleece for chillier moments and a warmer synthetic layer for cold days/emergencies, chosen based on the forecast. I also pack a waterproof/windproof jacket and waterproof/windproof trousers - light enough that it doesn’t bother me to have in my pack. I then swap the rain trousers for burlier ones if constant rain is forecasted.

This setup has seen me through many a hike, but everyone is different! Customise for your needs and the day’s forecast. As a rule of thumb, if you are coming for a week of hiking in summer, bring base layers to be comfortable on sunny 20°C days and bring insulation and rain gear to stay warm and dry in a rainstorm, when the temperature can get down to 5°C. If you end up not needing the rain gear or warm layers then consider yourself lucky!

Thunderbolt and lightning, very very frightening

Heavy rain often comes with thunderstorms - in fact the region around the north of the park is under thunderstorm advisory for 30% of the whole summer!

You do not want to be out on the exposed alpine plateaus as thunder starts cracking, so have an escape plan ready and turn back early. As is the norm with thunderstorms, they are more common in the afternoon and into the evening.

If you do find yourself caught in a thunderstorm, there is only one definitive way to keep yourself safe. Get under real cover - either in a building, a vehicle or uniform thick tree cover (rocks don’t count).

However, with little tree cover and huts few and far between, this is challenging in the Daisetsuzan. This is why it is so important to have the option of descending early, to watch the weather and to get off the mountain at the first sign of thunder.

The rain in Japan mainly falls on…

Another common question we get is, “Does Hokkaido have a rainy season?”. This is a good question as our hiking season overlaps with the June-July rainy season on mainland Japan. The good news is that the answer is no, there is no rainy season in Hokkaido. In fact as the table above shows, there are less hours of rainfall in summer than other seasons.

However, there are two caveats to this. Firstly, as discussed above, when it rains in summer, it pours. The amount of precipitation is actually higher in summer than other seasons, despite there being less hours of rainfall.

The other caveat is; while we don’t get the seasonal rain that stretches across mainland Japan, those weather systems push clouds up to Hokkaido. This is one of the reasons that the summer months see less sunshine than the shoulder season.

Autumn in the Daisetsuzan means two things - autumn colours and the first snowfall. Often, these happen at the same time.

September is one of my favourite months. The air feels crisper and cooler, but it’s still not too cold. October on the other hand is a transition month. The first snow has usually fallen and if it hasn’t settled too much, it’s a nice month to wrap up and enjoy one last hike before winter. But often, winter takes hold early and the upper mountains are blanketed in white. While pretty, this snow adds an extra challenge - you can’t see where you are putting your feet. While the surface appears smooth, the snow is still soft and you will step through to the rocky trail below, making for awkward travel.

My layering in September doesn’t actually change much from summer, but the fleece is always on and the insulation layer is always my warm one. A warm hat and gloves also find their way into my pack.

With October seeing a return to winter–like conditions, I will swap my base layer for a warm merino one and add ski gloves, a neck warmer and waterproof gaiters to my set up. Although in all honesty, once the snow settles I usually just hike at lower elevations where the trees still have their autumn colours.

A Tapestry of Colour

The dropping temperature in September prompts the start of the autumn colour season. The dates vary by a week or two every year, but the first leaves that change are the low shrubs, such as Lingonberry and Aleutian Avens found above 1500m, that turn a deep red in mid-September.

The Rowan then follow, also turning red, before the colour washes down the mountain from late September into mid–October. The trails at Daisetsu Kogen Onsen are one of my favourite places to see this seasonal palette.

Let It Snow

Hot on the heels of the autumn colours comes the first snow. It often snows at Mt. Asahidake before it does at Mt Fuji, with the first dusting coming mid to late September. In fact, the latest on record was the 15th of October.

Sometimes this first blast of winter will melt away, but sometimes it stays cold and the snowline moves progressively lower with each storm. At Bougakudai, which sits at 1000m in the Mt. Tokachi area, there is snow on the ground by the end of October more years than not and it’s rare for it to be clear by mid–November.

As autumn finishes, the hiking trails disappear under the snow, followed by the access roads for trailheads and Hokkaido’s long winter settles in.

Yep, you read that table right, winter is 5 months long in the Daisetsuzan! From November, the temperature starts rapidly dropping, with temperatures below -20°C common at the summit of Mt. Asahidake by January.

Needless to say, hiking in your regular gear would be an unpleasant experience. On top of the cold temperatures, the snow is light and fluffy and you will quickly find yourself sinking waist-deep. However, snowshoes provide a solution for this, allowing you to walk on top of the snow instead of through it. If snowshoeing is new to you, Michael does a great job of explaining everything you need to know about snowshoeing in his blog.

So, armed with a pair of snowshoes and wrapped up warm it is still possible to explore the Daisetsuzan on foot. In fact, with metres of snow burying all the bush, you can visit places impossible to reach when the snow has melted. The flip side to this is that snowshoeing in marginal snow is equal parts unpleasant and dangerous. This means that November into December is a time to give the hiking trails up in the Daisetsuzan a break and wait for the snow to pile up a bit more.

A Frozen Monsoon

But why does it snow so much here? Despite being at the same latitude as the French Riviera, the temperature in Hokkaido rarely gets above freezing all winter.

This is caused by strong northwest winds bringing cold air down from Siberia. These same winds pick up moisture as they travel across the sea, which brings large amounts of snowfall to the mountains. This is literally a sub-zero monsoon, which might help you to picture just how much it snows here.

Many of our guests ask what the weather will be like during their trip. Until now, we've only had seasonal trends for low-lying regions such as Asahikawa city to reference. This is the same with most weather apps. However, the weather atop Mt. Asahidake, Hokkaido's highest peak, can be vastly different despite its proximity to Asahikawa.

For example, it is early July and you wake up to sunny, 20°C weather in town. The forecast shows 25°C with afternoon showers and light wind, so you set off in shorts and a sun shirt, packing a light rain jacket just in case. The catch is, that forecast is for Asahikawa and not Mt. Asahidake.

An hour and a half later, you step out of the ropeway at 1600m to a refreshing, cool wind. The wind keeps you cool as you hike up the steep exposed ridge. Disappointingly, the summit disappears in cloud, but you’ve come this far so you push on!

You reach Hokkaido's summit and the wind is strong. With wind chill, the temperature is just 9°C and you cool down quickly now you’ve stopped. Skipping lunch, you start descending as rain begins. It quickly turns into a sideways downpour. Your jacket is no match and you're drenched and shivering, burning energy to stay warm. You run out of steam and turn to the weird looking chocolate bar you brought - which turns out to be red bean paste. Still, you force it down to get the calories you need to make it back, exhausted, grateful for an onsen and perhaps a little humbled.

If you've spent time in the mountains, this tale is familiar. Despite this, plenty of people don’t get the message. Exposure is a real risk in any season and sadly, people pass away every year.

That said, with a little preparation and erring on the side of caution, it is avoidable. Checking a forecast you know applies to the mountains is the best start. For English forecasts, we recommend yr.no for an easy overview or my current go to; Meteoblue.com. Windy.com is a good resource for going from big scale to small scale, but be warned - their temperature forecasts are not corrected for elevation and can be off by up to 5°C.

It also helps to check out reports from people who have done the hike recently or in the same season. Hokkaido Wilds is the best English language resource, they feature a vast collection of hikes across Hokkaido. However, make sure you check the “We visited this route on” note to be sure their experience matches your planned dates.

For more recent information I’ll check out trip reports on Japanese hiking site Yamap. While the site is in Japanese, you should be able to find your way through with the help of translation and the pictures will tell you more than the text. Just make sure you’re looking at the correct mountain, there are at least 20 Mt. Asahis across Japan for example!

There is one more trend I picked up in the data I’ve used for this post. Like much of the world, the Daisetsuzan is getting warmer. While this trend doesn’t surprise me, it is visible in the changing vegetation and summers in recent years have also been warmer than the averages listed above. The amount of warming did surprise me and it is definitely food for thought.

Hopefully, this blog gives you a good idea of what weather you can expect when you come hiking in the Daisetsuzan mountains. While the weather can be unpredictable and challenging at times, this variation is one of the reasons why I love hiking in the Daisetsuzan National Park.