Iwai weather in December

In December, Iwai sees average daytime highs of 11°C and overnight lows near 3°C, with 56 mm of precipitation across 6.8 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 13°C in the first days to 10°C by the end. The sky is clear or mostly clear about 58% 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 Iwai's 2nd-clearest and 11th-windiest month. For the whole year in context, see Iwai's year-round climate.

Daytime high
11°
10th warmest
Overnight low
3rd coldest
Precipitation
56 mm
6.8 wet days
Daylight
9 h 36 min
6:50 AM – 4:23 PM
Cloud cover
39%
2nd clearest
Wind
9 km/h
11th windiest
Solar energy
2.36 kWh/m²
Travel score
3.2
out of 10

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 13°C in the first days to 10°C by the end.

A typical December day in Iwai reaches about 11°C in the afternoon and slips back to 3°C overnight — a 8°C spread between the day's warmth and the night's chill. On most days the high lands between 8°C and 15°C. Set against its neighbours, December runs about 5°C cooler than November and about 2°C warmer than January.

-5°10°15°20°151015202531
Avg high (°C)Avg low (°C)
1135
2135
3135
4135
5135
6124
7124
8124
9124
10124
11123
12123
13113
14113
15113
16113
17113
18112
19112
20112
21112
22102
23102
24102
25102
26102
27101
28101
29101
30101
31101

How December really feels in Iwai

Once humidity and wind are folded in, December averages 0 days that feel above 32°C and 16 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
16
wind chill below the day's low

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

Iwai 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 / 606.51.29.82.0
Feb10° / 587.21.710.62.3
Mar13° / 10611.60.911.73.7
Apr18° / 10°10611.30.112.95.6
May23° / 15°13112.4013.96.3
Jun26° / 19°15414.9014.45.5
Jul29° / 23°16315.4014.24.5
Aug31° / 24°12313.6013.44.2
Sep27° / 20°16713.9012.25.5
Oct21° / 14°18612.5011.16.2
Nov16° / 859.1010.15.3
Dec11° / 566.80.19.63.2

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 58% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 13% of December, with mostly cloudy or overcast conditions the remaining 29%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16139
26337
36337
46436
56535
66634
76733
86832
96832
107030
117129
127129
137129
147228
157228
167228
177327
187327
197327
207327
217426
227426
237426
247426
257525
267525
277525
287624
297723
307723
317822

Chance of precipitation in December

Any precipitation

Iwai gets around 56 mm of rain and snow over 6.8 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 22% and peaks near 29% on the wettest days, and about 0 day brings snow. The odds ease toward the end of the month.

0%10%20%30%40%151015202531
Rain chance (%)
129
228
328
428
527
627
726
826
925
1024
1123
1223
1322
1422
1521
1621
1720
1820
1919
2019
2119
2219
2318
2418
2518
2617
2717
2817
2917
3017
3117

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 (%)Comfortable (%)
1982
2991
3991
4991
5991
6991
7991
81000
91000
101000
111000
121000
131000
141000
151000
161000
171000
181000
191000
201000
211000
221000
231000
241000
251000
261000
271000
281000
291000
301000
311000

Wind in December

Winds average 9 km/h in December.

Across December, daily wind ranges from about 9 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (km/h)Feels
19calm
29calm
39calm
49calm
59calm
69calm
79calm
89calm
99calm
109calm
119calm
129calm
139calm
149calm
159calm
169calm
179calm
189calm
199calm
2010calm
2110calm
2210calm
2310calm
2410calm
2510calm
2610calm
2710calm
2810calm
2910calm
3010calm
3110calm

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 6:38 AM to 6:56 AM, and sunset from 4:22 PM to 4:31 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.76:384:22
29.76:394:22
39.76:404:22
49.76:414:22
59.76:424:22
69.76:434:22
79.66:434:22
89.66:444:22
99.66:454:22
109.66:464:22
119.66:464:22
129.66:474:22
139.66:484:23
149.66:484:23
159.66:494:23
169.66:504:23
179.66:504:24
189.66:514:24
199.66:514:24
209.56:524:25
219.56:524:25
229.56:534:26
239.56:534:26
249.56:544:27
259.66:544:27
269.66:554:28
279.66:554:28
289.66:554:29
299.66:564:30
309.66:564:30
319.66:564:31

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 2.36 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 2.36 kWh/m² to a high of 5.12 kWh/m² in May across the year — December's 2.36 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
12.3Moderate
22.3Moderate
32.3Moderate
42.3Moderate
52.3Moderate
62.3Moderate
72.3Moderate
82.3Moderate
92.3Moderate
102.3Moderate
112.3Moderate
122.3Moderate
132.3Moderate
142.4Moderate
152.4Moderate
162.4Moderate
172.4Moderate
182.4Moderate
192.4Moderate
202.4Moderate
212.5Moderate
222.5Moderate
232.5Moderate
242.5Moderate
252.5Moderate
262.6Moderate
272.6Moderate
282.6Moderate
292.6Moderate
302.6Moderate
312.7Moderate
Planning a trip in December

Hazard calendar for Iwai

In seasonPeak

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

Iwai 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 Iwai?

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

3.2
Sightseeing
10th-best month of the year
0.0
Beach & pool
10th-best month of the year

December is a weaker month for outdoor sightseeing in Iwai.

What to pack for Iwai in December

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

In December, Iwai sees daytime highs around 11°C and nights near 3°C. Pack a warm layer. About 7 days see rain.

a warm layer

Sea temperature near Iwai 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 47 km away) is warmest in August at about 26°C and coldest in February near 13°C.

It's comfortable for a long swim from Jun 7 to Nov 3 — about 4.9 months when the water holds above 20°C.

10°15°20°25°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan14Bracing
Feb13Bracing
Mar13Bracing
Apr15Cool
May18Cool
Jun21Refreshing
Jul23Refreshing
Aug26Warm
Sep25Warm
Oct22Refreshing
Nov19Cool
Dec16Cool

UV index in Iwai 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 Iwai peaks around July 21 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 21UV 10Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar4Moderate
Apr6High
May8Very high
Jun9Very high
Jul10Very high
Aug10Very high
Sep9Very high
Oct6High
Nov3Moderate
Dec2Moderate

Air quality in Iwai 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 Iwai is worst in March — around 25 µg/m³ PM2.5 (moderate), about 1.8× the cleanest month (December, 14 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateMar 2425 µg/m³Dec 1914 µg/m³
PM2.5 (µg/m³)Level
Jan15Moderate
Feb18Moderate
Mar25Moderate
Apr25Moderate
May24Moderate
Jun19Moderate
Jul16Moderate
Aug15Moderate
Sep15Moderate
Oct16Moderate
Nov16Moderate
Dec14Moderate
Location & terrain

Where is Iwai?

Iwai sits at 36.0°N, 139.9°E, 5 m above sea level, in Japan. The nearest listed city is Bandō, 4.0 km away.

Topography around Iwai

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

Within 3 km, the terrain around Iwai has only modest variations in elevation — a maximum elevation change of 32 m around an average of 17 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 48 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,630 m.

The land around Iwai is covered by artificial surfaces (34%), trees (30%) and cropland (26%) within 3 km, cropland (43%) and artificial surfaces (31%) within 16 km, and trees (36%), artificial surfaces (29%) and cropland (22%) within 80 km.

3 km
32 m
16 km
48 m
80 km
1,630 m
treesgrasslandcroplandartificial surfacesbare terrainwater
December weather nearby: Bandō 4.0 km · Jōsō 6.0 km · Mitsukaidō 8.0 km · Ishige 10 km · Sakai 11 km · Noda 12 km · Tsukubamirai 12 km · Yachiyo 15 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 Iwai (36.05°, 139.9°, elevation 5 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).