Karuizawa weather in December

In December, Karuizawa sees average daytime highs of 6°C and overnight lows near -1°C, with 49 mm of precipitation across 7.6 wet days and about 9.6 hours of daylight. It is the 10th-warmest and 12th-wettest month of the year here.

Highs ease over the month, from about 8°C in the first days to 4°C by the end. The sky is clear or mostly clear about 49% of the time in December, and the air most often feels dry.

Daylight stretches from about 9 h 42 min at the start of December to 9 h 36 min by month's end. Set against the rest of the year, December is Karuizawa's 1st-clearest and 3rd-windiest month. For the whole year in context, see Karuizawa's year-round climate.

Daytime high
10th warmest
Overnight low
-1°
3rd coldest
Precipitation
49 mm
7.6 wet days
Daylight
9 h 30 min
6:56 AM – 4:28 PM
Cloud cover
45%
1st clearest
Wind
8 km/h
3rd windiest
Solar energy
2.51 kWh/m²
Travel score
0.6
out of 10

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 8°C in the first days to 4°C by the end.

A typical December day in Karuizawa reaches about 6°C in the afternoon and slips back to -1°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 2°C and 10°C. Set against its neighbours, December runs about 5°C cooler than November and about 3°C warmer than January.

-10°-5°10°15°151015202531
Avg high (°C)Avg low (°C)
191
281
381
480
580
680
770
870
970
107-1
117-1
126-1
136-1
146-1
156-1
166-1
176-2
186-2
195-2
205-2
215-2
225-2
235-2
245-2
255-2
265-3
275-3
284-3
294-3
304-3
314-3

How December really feels in Karuizawa

Once humidity and wind are folded in, December averages 0 days that feel above 32°C and 31 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
31
wind chill below the day's low

The story in December is cold — wind chill drags the overnight "feels like" below the raw low.

Karuizawa weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 12th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -4°597.46.59.80.0
Feb / -4°608.66.710.60.0
Mar / -1°11013.17.111.71.3
Apr14° / 12213.82.112.93.7
May19° / 10°16516.80.113.95.1
Jun21° / 15°25422.7014.44.3
Jul25° / 19°28224014.24.5
Aug26° / 19°24024.1013.44.5
Sep22° / 16°24120.6012.24.8
Oct17° / 19515.5011.14.7
Nov11° / 728.80.610.13.1
Dec / -1°497.64.49.60.6

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 49% of the time in December, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 20% of December, with mostly cloudy or overcast conditions the remaining 31%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16436
26436
36436
46436
56535
66634
76634
86634
96634
106733
116733
126832
136832
146832
156931
166931
176832
186931
196931
207030
217030
227228
237228
247327
257327
267327
277426
287426
297426
307426
317426

Chance of precipitation in December

Any precipitationSnow

Karuizawa gets around 49 mm of rain and snow over 7.6 wet days in December, the driest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 24% and peaks near 28% on the wettest days, and about 4 days bring snow. The odds ease toward the end of the month.

0%10%20%30%40%151015202531
Rain chance (%)Snow chance (%)
1288
2289
32810
42810
52811
62811
72712
82712
92712
102613
112613
122513
132513
142513
152413
162413
172313
182313
192314
202214
212214
222215
232215
242115
252116
262116
272016
282016
292017
302017
312017

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

Most of December feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, December lands in the dry band about 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)
1100
2100
3100
4100
5100
6100
7100
8100
9100
10100
11100
12100
13100
14100
15100
16100
17100
18100
19100
20100
21100
22100
23100
24100
25100
26100
27100
28100
29100
30100
31100

Wind in December

Winds average 8 km/h in December.

Across December, daily wind ranges from about 7 km/h on the calmest days to 9 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (km/h)Feels
17calm
27calm
37calm
47calm
57calm
67calm
78calm
88calm
98calm
108calm
118calm
128calm
138calm
148calm
158calm
168calm
178calm
188calm
198calm
208calm
218calm
228calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm
319calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 9 h 42 min at the start of December to 9 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 6 minutes over December. Sunrise moves from 6:44 AM to 7:02 AM, and sunset from 4:26 PM to 4:35 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.76:444:26
29.76:454:26
39.76:464:26
49.76:474:26
59.66:484:26
69.66:484:26
79.66:494:26
89.66:504:26
99.66:514:26
109.66:524:26
119.66:524:26
129.66:534:27
139.66:544:27
149.56:544:27
159.56:554:27
169.56:564:28
179.56:564:28
189.56:574:28
199.56:574:29
209.56:584:29
219.56:584:30
229.56:594:30
239.56:594:30
249.57:004:31
259.57:004:32
269.57:014:32
279.57:014:33
289.57:014:33
299.57:024:34
309.57:024:35
319.67:024:35

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 2.51 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 2.51 kWh/m² to a high of 5.52 kWh/m² in May across the year — December's 2.51 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
12.5Moderate
22.5Moderate
32.5Moderate
42.5Moderate
52.5Moderate
62.5Moderate
72.5Moderate
82.5Moderate
92.5Moderate
102.5Moderate
112.5Moderate
122.5Moderate
132.5Moderate
142.5Moderate
152.5Moderate
162.5Moderate
172.5Moderate
182.5Moderate
192.5Moderate
202.6Moderate
212.6Moderate
222.6Moderate
232.6Moderate
242.6Moderate
252.6Moderate
262.6Moderate
272.7Moderate
282.7Moderate
292.7Moderate
302.7Moderate
312.7Moderate
Planning a trip in December

Hazard calendar for Karuizawa

In seasonPeak

None of Karuizawa's seasonal hazards are active in December. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Karuizawa's rainy season runs May–October, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is December a good time to visit Karuizawa?

Our two travel scores rate December for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

0.6
Sightseeing
10th-best month of the year
0.0
Beach & pool
9th-best month of the year

December is a weaker month for outdoor sightseeing in Karuizawa.

What to pack for Karuizawa in December

From December's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In December, Karuizawa sees daytime highs around 6°C and nights near -1°C. Pack a warm layer. Worth having: a heavy coat. About 8 days see rain.

a warm layera heavy coat

UV index in Karuizawa in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 2. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Karuizawa peaks around July 18 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateJul 18UV 10Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar6High
Apr7High
May8Very high
Jun9Very high
Jul10Very high
Aug9Very high
Sep9Very high
Oct6High
Nov3Moderate
Dec2Moderate

Air quality in Karuizawa in December

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where December falls, not just the annual average.

Air quality in Karuizawa is worst in April — around 21 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (December, 10 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodApr 1821 µg/m³Dec 1810 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar19Moderate
Apr21Moderate
May20Moderate
Jun18Moderate
Jul15Moderate
Aug14Moderate
Sep13Moderate
Oct12Moderate
Nov11Good
Dec10Good
Location & terrain

Where is Karuizawa?

Karuizawa sits at 36.4°N, 138.6°E, 952 m above sea level, in Japan. The nearest listed city is Miyota, 11 km away.

Topography around Karuizawa

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Karuizawa.

Within 3 km, the terrain around Karuizawa has large variations in elevation — a maximum elevation change of 632 m around an average of 1,004 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,316 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,985 m.

The land around Karuizawa is covered by trees (86%) within 3 km, trees (86%) within 16 km, and trees (80%) within 80 km.

3 km
632 m
16 km
2,316 m
80 km
2,985 m
treesgrasslandcroplandartificial surfacesbare terrainwater
December weather nearby: Miyota 11 km · Komoro 18 km · Saku 20 km · Annaka 24 km · Tōmi 24 km · Tomioka 26 km · Ueda 32 km · Nakanojō 32 km

Japan travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type A / B
100 V · 50 / 60 Hz
Prices
≈ 65% of US
price level, 2025
GDP per capita
$35,951
2025
Happiness
6.1 / 10
World Happiness, 2025
Safe drinking water
99%
of population, 2024
Homicide rate
0.2
per 100k, 2023
Road deaths
3.6
per 100k/yr, 2019
Income group
High
World Bank
English
Very low
EF EPI 446
Religion
Shintoism 49%Buddhism 46%other 4%Christianity 1%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Karuizawa (36.35°, 138.6333°, elevation 952 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).