Ōmachi weather in December

In December, Ōmachi sees average daytime highs of -2°C and overnight lows near -8°C, with 196 mm of precipitation across 21.4 wet days and about 9.6 hours of daylight. It is the 10th-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 1°C in the first days to -4°C by the end. The sky is clear or mostly clear about 17% 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 30 min by month's end. Set against the rest of the year, December is Ōmachi's 6th-clearest and 4th-windiest month. For the whole year in context, see Ōmachi's year-round climate.

Daytime high
-2°
10th warmest
Overnight low
-8°
3rd coldest
Precipitation
196 mm
21.4 wet days
Daylight
9 h 30 min
6:59 AM – 4:30 PM
Cloud cover
71%
6th clearest
Wind
7 km/h
4th windiest
Solar energy
2.39 kWh/m²
Travel score
0.0
out of 10

Ōmachi is dissolved municipality in Kitaazumi district, Nagano prefecture, Japan.

Founded
1889

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 1°C in the first days to -4°C by the end.

A typical December day in Ōmachi reaches about -2°C in the afternoon and slips back to -8°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between -6°C and 3°C. Set against its neighbours, December runs about 7°C cooler than November and about 3°C warmer than January.

-15°-10°-5°10°151015202531
Avg high (°C)Avg low (°C)
12-6
22-6
31-6
41-6
51-6
61-7
70-7
80-7
90-7
10-1-7
11-1-8
12-1-8
13-1-8
14-1-8
15-2-8
16-2-8
17-2-9
18-2-9
19-2-9
20-2-9
21-2-9
22-3-9
23-3-9
24-3-9
25-3-10
26-3-10
27-3-10
28-3-10
29-4-10
30-4-10
31-4-10

How December really feels in Ōmachi

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
25 feel bitter (≤ -10°C)

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

Ōmachi weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-5° / -11°19322.4249.80.0
Feb-3° / -10°16718.319.610.60.0
Mar / -6°2111919.111.70.0
Apr / -1°20016.69.912.90.9
May14° / 23717.81.313.93.5
Jun18° / 11°34420.6014.44.1
Jul22° / 15°45124.4014.24.3
Aug23° / 16°29721.9013.44.9
Sep19° / 12°29219.1012.24.6
Oct13° / 22716.31.111.13.2
Nov / -2°18317.311.110.10.6
Dec-2° / -8°19621.421.49.60.0

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 17% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 10% of December, with mostly cloudy or overcast conditions the remaining 74%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13169
22971
32971
42971
52872
62872
72872
82872
92872
102674
112674
122674
132674
142674
152674
162674
172674
182674
192773
202773
212773
222773
232773
242575
252575
262575
272575
282476
292377
302377
312377

Chance of precipitation in December

Any precipitationSnow

Ōmachi gets around 196 mm of rain and snow over 21.4 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 69% and peaks near 72% on the wettest days, and about 21 days bring snow. The odds climb toward the end of the month.

0%20%40%60%80%151015202531
Rain chance (%)Snow chance (%)
16457
26558
36560
46661
56662
66763
76764
86865
96866
106867
116968
126969
136969
146970
156970
166970
176971
186971
196971
207072
217072
227072
237073
247073
257073
267073
277174
287174
297174
307174
317275

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 7 km/h in December.

Across December, daily wind ranges from about 6 km/h on the calmest days to 7 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (km/h)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm
317calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 9 h 42 min at the start of December to 9 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 12 minutes over December. Sunrise moves from 6:48 AM to 7:06 AM, and sunset from 4:29 PM to 4:38 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.76:484:29
29.76:484:29
39.76:494:29
49.66:504:29
59.66:514:29
69.66:524:29
79.66:534:29
89.66:534:29
99.66:544:29
109.66:554:29
119.66:564:29
129.56:564:29
139.56:574:30
149.56:584:30
159.56:584:30
169.56:594:30
179.57:004:31
189.57:004:31
199.57:014:31
209.57:014:32
219.57:024:32
229.57:024:33
239.57:034:33
249.57:034:34
259.57:044:34
269.57:044:35
279.57:044:35
289.57:054:36
299.57:054:37
309.57:054:37
319.57:064:38

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 2.39 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 2.39 kWh/m² to a high of 5.74 kWh/m² in May across the year — December's 2.39 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
12.5Moderate
22.4Moderate
32.4Moderate
42.4Moderate
52.4Moderate
62.4Moderate
72.4Moderate
82.4Moderate
92.4Moderate
102.4Moderate
112.4Moderate
122.4Moderate
132.4Moderate
142.4Moderate
152.4Moderate
162.4Moderate
172.4Moderate
182.4Moderate
192.4Moderate
202.4Moderate
212.4Moderate
222.4Moderate
232.4Moderate
242.4Moderate
252.4Moderate
262.5Moderate
272.5Moderate
282.5Moderate
292.5Moderate
302.5Moderate
312.5Moderate
Planning a trip in December

Hazard calendar for Ōmachi

In seasonPeak

In December, Ōmachi sits inside its pacific typhoon season. The full year is below, with each hazard's peak months called out.

Ōmachi sits in the Pacific typhoon belt; the season peaks July–October.

Pacific typhoon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is December a good time to visit Ōmachi?

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

0.0
Sightseeing
9th-best month of the year
0.0
Beach & pool
7th-best month of the year

December is a weaker month for outdoor sightseeing in Ōmachi.

What to pack for Ōmachi in December

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

In December, Ōmachi sees daytime highs around -2°C and nights near -8°C. Pack a warm layer, a heavy coat and rain gear. About 21 days see rain.

a warm layera heavy coatrain gear

Sea temperature near Ōmachi in December

The nearest coast averages about 16°C in December — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 61 km away) is warmest in August at about 27°C and coldest in March near 10°C.

It's comfortable for a long swim from Jun 18 to Nov 3 — about 4.6 months when the water holds above 20°C.

10°20°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan13Bracing
Feb11Bracing
Mar10Bracing
Apr11Bracing
May15Cool
Jun20Cool
Jul24Refreshing
Aug27Warm
Sep25Warm
Oct22Refreshing
Nov19Cool
Dec16Cool

UV index in Ōmachi 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 Ōmachi peaks around July 20 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 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 highExtremeVery highModerateJul 20UV 10Dec 21UV 2
UV index (midday)Level
Jan3Moderate
Feb5Moderate
Mar6High
Apr7Very high
May9Very high
Jun10Very high
Jul10Extreme
Aug10Extreme
Sep9Very high
Oct6High
Nov3Moderate
Dec2Moderate

Air quality in Ōmachi 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 Ōmachi 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 1721 µg/m³Dec 1510 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar20Moderate
Apr21Moderate
May20Moderate
Jun18Moderate
Jul15Moderate
Aug13Moderate
Sep12Good
Oct11Good
Nov11Good
Dec10Good
Location & terrain

Where is Ōmachi?

Ōmachi sits at 36.5°N, 137.9°E, 714 m above sea level, in Japan. The nearest listed city is Hotaka, 18 km away.

Topography around Ōmachi

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

Within 3 km, the terrain around Ōmachi has significant variations in elevation — a maximum elevation change of 486 m around an average of 823 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,371 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,120 m.

The land around Ōmachi is covered by trees (50%) and artificial surfaces (26%) within 3 km, trees (83%) within 16 km, and trees (75%) within 80 km.

3 km
486 m
16 km
2,371 m
80 km
3,120 m
treesgrasslandcroplandartificial surfacesbare terrainwater
December weather nearby: Hotaka 18 km · Chikuma 20 km · Toyoshina 22 km · Azumino 24 km · Sakaki 29 km · Matsumoto 31 km · Nagano 33 km · Ueda 39 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 Ōmachi (36.5°, 137.8667°, elevation 714 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. 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).