Hakone Weather in September

Season: early autumn
Climate Overview: turn cool gradually, rain occasionally, possible typhoons

Mount Fuji Seen from Hakone in Autumn

Temperature

Average Temperature: 23.2℃ (73.8℉)
Average High Temperature: 27.7℃ (81.9℉), the highest in record is 35.5℃ (95.9℉)
Average Low Temperature: 19.1℃ (66.4℉), the lowest in record is 14.2℃ (57.6℉)

Hakone’s temperature in September shows a downward trend: it is still a little hot in the beginning of the month but turns cool gradually. The highest temperatures for most days are around 30℃ (86℉), and very a few days can even reach over 34℃ (93.2℉). In the second half, the temperature is mild. Then, there is a huge temperature difference between day and night, and you feel a little cold in the early morning and at night.

In addition, the temperature this month is not stable. Rise and fall are common because of rainfall and typhoon. On some days, the highest temperature is about 32℃ (89.6℉), while on another day, it may be only about 22℃ (71.6℉). Therefore, apart from summer clothes, you’d better also pack a set of autumn clothes in your luggage.

Rainfall

Average Rainfall: 151mm
Average Rainy Days: 7 days

As a whole, rainfall is not a big issue for a Hakone trip in September. But heavy rain happens occasionally. For example, sometimes, the rainfall in 24 hours exceed 80mm. In that case, any travel plan for outdoor activities would be ruined. But, visitors don’t need to worry too much, because the chance is not high. In recent years, there were only 1 - 3 such days, which can be easily avoided by checking weather forecast. In addition, it should be noted that typhoon may strike Hakone in September, which also needs your prior attention.

Sunset, Sunrise, Day Length

Sunrise (1st - 30th): roughly 5:15 - 5:35
Sunset (1st - 30th): roughly 18:10 - 17:30
Average Day Length: 12h25min

In September, it dawns later and later and gets darks earlier and earlier, which means the time for day time sightseeing reduces.

The UV index this month is 5 - a middle level, which requires sun protection measures.

How to Dress in Hakone in September

Upper: Blouse, T-shirt, and other loose clothes are all suitable. Girls can also wear long-sleeve dresses. Also, you’d better take a thin shirt. In the early morning or when the temperature drops, it may be a little cold. At noon when the sunshine is burning, you can also use the shirt to protect your skin.

Lower: Shorts and thin long pants are both fine. If you plan to go to the forests or to hike, maybe the long pants are better. Because in this month, there are still mosquitos. In addition, some plants have sharp edges and they would hurt you.

Shoes: For indoor attractions, sandals, and casual shoes are not bad. For outdoor places, non-slippery shoes like breathable hiking shoes are better, especially after the rain, because the mountain roads can be muddy and slippery.

Other Necessities:

1. Sun protection products: sunscreen cream, sunglasses, and hat
2. Umbrella
3. Cold medicines: You may get cold because of the huge temperature difference between day and night in this month
4. Mosquito repellent: In mountains, there are still many mosquitos this month.
5. Band-Aids: The occasional rain makes the mountain road muddy and slippery. Take some band-aids in case you fall down and get hurt.

Top Things to Do in Hakone in September 2025

Without that burning temperature like in August and less tourists, September is a good time for traveling here and there in Hakone.

1. Watch Volcano Activities in Owakudani Valley

Taking Hakone Ropeway, you watch this 3,000-year-old volcano surrounded by the white water stream from hot springs and yellow sulfur. To observe the volcano, you can also walk along the Nature Walking Trail by making reservation in advance. There, you can see how the black eggs are made in hot springs and see the surface of volcano rocks.

Owakudani Valley

Tip: It is suggested to wear a face mask as the sulfur gas is pungent.

2. Watch Sculptures in Open Air Museum

Open Air Museum is one of the must-visit attractions in Hakone. It combines natural beauty and sculpture art perfectly. There are about 120 sculptures scattered outdoor across the garden which visitors can observe at a close distance. In addition, the Museum stores the works of some world-famous masters like Picasso and Henry Moore.

Open Air Museum in Autumn

3. Watch susuki grass in Sengokuraha

Like the hydrangea in June, Sengokuhara’s susuki grass in September is a highlight of autumn in Hakone. From late September to early November, the susuki grass with the height of an adult would turn from green into golden color. Walking along the trail on the mountain, you can observe this plant at close distance.

Susuki Grass in Sengokuhara in September

Tips

1. If heavy typhoon happens, the onsen distribution system may be influenced. Sometimes, the onsen hotels even stop service. It is suggested to consult the onsen hotel in advance before making a reservation.

2. September is the shoulder season of Hakone and the advantage of going there during the period are the fewer tourists, lower accommodation cost, and better traveling experience.

September Weather for Other Cities in Japan:

Hakone Weather by Month

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