Iwamizawa weather in December

In December, Iwamizawa sees average daytime highs of 0°C and overnight lows near -7°C, with 69 mm of precipitation across 15.3 wet days and about 8.9 hours of daylight. It is the 10th-warmest and 7th-wettest month of the year here.

Highs ease over the month, from about 2°C in the first days to -2°C by the end. The sky is clear or mostly clear about 10% of the time in December, and the air most often feels dry.

Daylight stretches from about 9 hours at the start of December to 8 h 48 min by month's end. Set against the rest of the year, December is Iwamizawa's 9th-clearest and 6th-windiest month. For the whole year in context, see Iwamizawa's year-round climate.

Daytime high
10th warmest
Overnight low
-7°
3rd coldest
Precipitation
69 mm
15.3 wet days
Daylight
8 h 48 min
7:05 AM – 3:54 PM
Cloud cover
69%
9th clearest
Wind
11 km/h
6th windiest
Solar energy
1.6 kWh/m²
Travel score
0.0
out of 10

Iwamizawa is city in Hokkaido, Japan.

Density
177/km²
people per km²
Founded
1943

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 2°C in the first days to -2°C by the end.

A typical December day in Iwamizawa reaches about 0°C in the afternoon and slips back to -7°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between -4°C and 5°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)
13-4
23-4
32-4
42-4
52-5
62-5
71-5
81-5
91-6
101-6
111-6
120-6
130-6
140-7
150-7
160-7
170-7
180-7
19-1-7
20-1-8
21-1-8
22-1-8
23-1-8
24-1-8
25-1-8
26-1-8
27-1-8
28-1-8
29-1-8
30-2-8
31-2-9

How December really feels in Iwamizawa

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
24 feel bitter (≤ -10°C)

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

Iwamizawa weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-3° / -10°4912.718.19.20.0
Feb-2° / -9°4210.714.910.20.0
Mar / -5°5711.610.511.60.1
Apr11° / 6711.83.313.12.5
May16° / 8411.40.114.44.9
Jun20° / 12°649.6015.16.1
Jul23° / 17°11311.6014.96.4
Aug24° / 18°16112.5013.86.3
Sep21° / 13°12613.2012.35.9
Oct15° / 9213.60.310.84.1
Nov / 8716.18.49.50.9
Dec / -7°6915.318.18.90.0

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 10% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 24% of December, with mostly cloudy or overcast conditions the remaining 66%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13466
23466
33367
43367
53367
63367
73466
83466
93367
103466
113466
123466
133466
143466
153565
163565
173565
183466
193466
203565
213565
223466
233466
243367
253367
263367
273268
283268
293268
303268
313268

Chance of precipitation in December

Any precipitationSnow

Iwamizawa gets around 69 mm of rain and snow over 15.3 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 49% and peaks near 53% on the wettest days, and about 18 days bring snow. The odds ease toward the end of the month.

0%20%40%60%151015202531
Rain chance (%)Snow chance (%)
15350
25351
35352
45253
55255
65255
75156
85157
95158
105158
115059
125059
135059
145060
155060
164960
174960
184960
194960
204960
214960
224960
234860
244860
254860
264760
274760
284660
294660
304660
314661

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 11 km/h in December.

Across December, daily wind ranges from about 10 km/h on the calmest days to 11 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (km/h)Feels
111calm
211calm
311calm
411calm
511calm
611calm
711calm
811calm
911calm
1011calm
1111calm
1211calm
1311calm
1411calm
1511calm
1610calm
1710calm
1810calm
1910calm
2010calm
2110calm
2210calm
2310calm
2410calm
2510calm
2610calm
2710calm
2810calm
2910calm
3010calm
3110calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 9 hours at the start of December to 8 h 48 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 6:52 AM to 7:11 AM, and sunset from 3:54 PM to 4:01 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.06:523:54
29.06:533:54
39.06:543:53
49.06:553:53
59.06:563:53
68.96:573:53
78.96:573:53
88.96:583:53
98.96:593:53
108.97:003:53
118.97:013:53
128.97:023:53
138.87:023:53
148.87:033:53
158.87:043:53
168.87:053:54
178.87:053:54
188.87:063:54
198.87:063:55
208.87:073:55
218.87:083:55
228.87:083:56
238.87:083:56
248.87:093:57
258.87:093:57
268.87:103:58
278.87:103:59
288.87:103:59
298.87:104:00
308.87:114:01
318.87:114:01

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 1.6 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 1.6 kWh/m² to a high of 5.38 kWh/m² in May across the year — December's 1.6 kWh/m² sits near the bottom.

00.511.522.5151015202531
Solar energy (kWh/m²)Level
11.6Dim
21.6Dim
31.6Dim
41.6Dim
51.6Dim
61.6Dim
71.6Dim
81.6Dim
91.6Dim
101.6Dim
111.6Dim
121.6Dim
131.6Dim
141.6Dim
151.6Dim
161.6Dim
171.6Dim
181.6Dim
191.6Dim
201.6Dim
211.6Dim
221.6Dim
231.7Dim
241.7Dim
251.7Dim
261.7Dim
271.7Dim
281.7Dim
291.8Dim
301.8Dim
311.8Dim
Planning a trip in December

Hazard calendar for Iwamizawa

In seasonPeak

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

Iwamizawa 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 Iwamizawa?

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

0.0
Sightseeing
10th-best month of the year
0.0
Beach & pool
8th-best month of the year

December is a weaker month for outdoor sightseeing in Iwamizawa.

What to pack for Iwamizawa in December

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

In December, Iwamizawa sees daytime highs around 0°C and nights near -7°C. Pack a warm layer, a heavy coat and rain gear. About 15 days see rain.

a warm layera heavy coatrain gear

Sea temperature near Iwamizawa in December

The nearest coast averages about 9°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 37 km away) is warmest in August at about 22°C and coldest in February near 5°C.

It's comfortable for a long swim from Jul 31 to Sep 22 — about 1.8 months when the water holds above 20°C.

10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan7Bracing
Feb5Bracing
Mar5Bracing
Apr7Bracing
May10Bracing
Jun14Bracing
Jul19Cool
Aug22Refreshing
Sep21Refreshing
Oct17Cool
Nov13Bracing
Dec9Bracing

UV index in Iwamizawa in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 1. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Iwamizawa peaks around August 18 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighHighVery highHighModerateLowAug 18UV 8Dec 19UV 1
UV index (midday)Level
Jan1Low
Feb3Moderate
Mar3Moderate
Apr6High
May7Very high
Jun7High
Jul5Moderate
Aug8Very high
Sep6High
Oct4Moderate
Nov2Low
Dec1Low

Air quality in Iwamizawa 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 Iwamizawa is worst in April — around 21 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (December, 9 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodApr 1220 µg/m³Dec 159 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb15Moderate
Mar20Moderate
Apr21Moderate
May19Moderate
Jun14Moderate
Jul13Moderate
Aug11Good
Sep11Good
Oct12Good
Nov10Good
Dec9Good
Location & terrain

Where is Iwamizawa?

Iwamizawa sits at 43.2°N, 141.8°E, 17 m above sea level, in Japan. The nearest listed city is Bibai, 16 km away.

Topography around Iwamizawa

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

Within 3 km, the terrain around Iwamizawa has only modest variations in elevation — a maximum elevation change of 101 m around an average of 24 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 559 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,032 m.

The land around Iwamizawa is covered by artificial surfaces (43%) and cropland (35%) within 3 km, cropland (54%) and trees (33%) within 16 km, and trees (64%) within 80 km.

3 km
101 m
16 km
559 m
80 km
2,032 m
treesgrasslandcroplandartificial surfaceswater
December weather nearby: Bibai 16 km · Tōbetsu 20 km · Ebetsu 20 km · Kitahiroshima 29 km · Ishikari 33 km · Sunagawa 34 km · Sapporo 36 km · Eniwa 37 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 Iwamizawa (43.2003°, 141.7597°, elevation 17 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).