Gunma Weather: Month-by-Month Climate Guide for Trip Planning

Gunma's Two Climate Zones: Lowlands vs Mountains

Gunma Prefecture (群馬県) has one of the most dramatic climate splits of any prefecture in Japan. The lowland cities — Maebashi (前橋市), Takasaki (高崎市), and Isesaki — sit on the Kanto Plain and experience some of Japan's most extreme summer heat. The mountain areas — Kusatsu (草津町) at approximately 1,200 meters elevation and Minakami (水上町) in the north — are cooler in summer and receive heavy snow in winter.

This means packing for a Gunma trip depends entirely on where you are going. A summer visit to Takasaki requires heat preparation similar to the hottest parts of Japan; a winter visit to Kusatsu requires snow gear. The same prefecture, same week, can differ by 10°C or more.

According to Climate Japan, the prefecture-wide averages — around 26°C (79°F) in summer and 3°C (38°F) in winter — mask this variation. For a broader weather overview, see our Gunma weather guide. For Kusatsu-specific conditions, see our Kusatsu weather guide.

Spring (March-May): Cherry Blossoms to Hiking Season

Spring in Gunma is the transition from cold to warm, with significant variation month to month:

Month	Lowland (Maebashi)	Mountain (Kusatsu)	Rainfall
March	5-14°C (41-57°F)	-3 to 5°C (27-41°F)	Low
April	10-20°C (50-68°F)	2-12°C (36-54°F)	Moderate
May	15-25°C (59-77°F)	7-17°C (45-63°F)	Moderate

Cherry blossoms typically peak in late March to early April in lowland areas. Mountain areas bloom later — Kusatsu does not see full blossoms until late April or early May.

May is one of the most pleasant months for visiting Gunma. Temperatures in both lowland and mountain areas are comfortable, rainfall is moderate, and the hiking season opens in mountain regions. For guidance on timing your visit, see our best time to visit Gunma guide.

Summer (June-August): Extreme Heat and Mountain Escapes

Lowland Heat Records and What to Expect

Gunma's lowland cities are among the hottest places in Japan during summer. According to Nippon.com, on August 5, 2025, Isesaki in Gunma Prefecture recorded 41.8°C (107.2°F) — the highest temperature ever recorded in Japan. This was not a freak event; lowland Gunma regularly sees mogusabi (猛暑日, days exceeding 35°C/95°F) throughout July and August.

According to Climate Japan, August also brings the heaviest rainfall at approximately 200mm, often in the form of intense afternoon thunderstorms. Pack waterproof clothing and plan outdoor activities for mornings.

If you are visiting lowland Gunma in summer, prepare for heat comparable to the worst of Tokyo or Osaka — and sometimes worse. Carry water, seek shade, and take breaks in air-conditioned spaces.

Mountain Areas as a Cool Refuge

Mountain towns like Kusatsu and Minakami are 5-10°C cooler than the lowlands. A day that hits 38°C in Takasaki might be 28-30°C in Kusatsu — still warm, but manageable. This is why summer onsen tourism to mountain areas has long been popular among Japanese visitors escaping the plains.

June brings the rainy season (tsuyu) to Gunma, with higher humidity and frequent overcast days across both zones. July and August are the hottest months, with the prefecture averaging about 26°C (79°F) overall according to Climate Japan.

Autumn (September-November): Best Weather for Travel

Autumn is arguably the best season to visit Gunma:

Month	Lowland (Maebashi)	Mountain (Kusatsu)	Conditions
September	20-28°C (68-82°F)	12-20°C (54-68°F)	Still warm, decreasing rain
October	14-22°C (57-72°F)	6-14°C (43-57°F)	Comfortable, autumn foliage begins
November	8-16°C (46-61°F)	0-8°C (32-46°F)	Cool, peak foliage

September can still be warm, particularly in lowland areas, and the tail end of typhoon season brings occasional storms. October and November offer comfortable temperatures across the prefecture with lower rainfall.

Autumn foliage is a major draw. Lowland areas see peak color in mid to late November; mountain areas color earlier, typically late October through mid-November. The combination of cool weather, clear skies, and fall colors makes October-November the most reliably pleasant months for Gunma travel.

Winter (December-February): Snow, Onsen, and Karakaze

Winter in Gunma divides sharply between the two climate zones:

Lowland cities experience mild but dry winters. According to Climate Japan, January, February, and December average about 3°C (38°F). Snow is rare in lowland areas, but the karakaze (からっ風) — a dry, cold north wind characteristic of Gunma — makes it feel significantly colder. The karakaze brings clear skies but strips moisture from the air, leaving skin and lips uncomfortably dry.

Mountain areas receive substantial snowfall. According to Climate Japan, February is the snowiest month with approximately 20cm of snow. Kusatsu and Minakami accumulate deeper snow due to their elevation, supporting ski resorts and creating the classic snow-covered onsen landscape.

For travelers heading to mountain onsen towns in winter, expect temperatures regularly below freezing, snow on roads, and the need for proper winter clothing. The combination of outdoor onsen (rotenburo) and fresh snowfall is one of Gunma's signature winter experiences.

What to Pack for Each Season

Spring (March-May):

• Layered clothing — mornings can be cold, afternoons warm
• Light jacket for mountain areas
• Rain layer for occasional spring showers

Summer (June-August):

• Lightweight, breathable clothing
• Waterproof jacket or umbrella (August thunderstorms)
• Sun protection: hat, sunscreen, refillable water bottle
• For mountain areas: long sleeves for cooler evenings

Autumn (September-November):

• Layers — comfortable in daytime, cool in evenings
• Warmer jacket for November, especially in mountain areas
• Rain gear for early September typhoon season

Winter (December-February):

• Warm coat, scarf, and gloves
• Moisturizer and lip balm (essential for karakaze dryness)
• For mountain areas: snow boots, thermal layers, waterproof outerwear
• For lowland areas: warm but lighter layers — cold and dry, not cold and wet

Frequently Asked Questions

How hot does it get in Gunma in summer?

Lowland cities like Isesaki and Takasaki regularly exceed 40°C (104°F). On August 5, 2025, Isesaki recorded 41.8°C (107.2°F) — the highest temperature ever recorded in Japan, according to Nippon.com. Mountain towns like Kusatsu at 1,200 meters elevation are 5-10°C cooler, typically reaching 28-30°C (82-86°F) on the hottest days.

Does it snow in Gunma?

Yes, in mountain areas. February averages about 20cm of snow across the prefecture, with Kusatsu and Minakami receiving heavier accumulations due to elevation. Lowland cities like Maebashi and Takasaki see little to no snow — winter there is cold and dry rather than cold and snowy.

When is the best weather for visiting Gunma?

October and November offer the most consistently pleasant conditions — comfortable temperatures, low rainfall, and autumn foliage. April and May are also excellent for cherry blossoms and the start of hiking season. Summer is extreme in lowland cities; winter requires snow preparation for mountain areas.

What is karakaze and how does it affect winter visits?

Karakaze (からっ風) is a dry, cold north wind that blows through Gunma in winter. It brings clear skies and sunshine but strips moisture from the air, causing dry skin, chapped lips, and a wind chill that makes temperatures feel colder than they are. Bring moisturizer and lip balm — they are not optional for winter Gunma trips.