Saikai weather in December

In December, Saikai sees average daytime highs of 12°C and overnight lows near 9°C, with 81 mm of rain across 9.2 wet days and about 9.9 hours of daylight. It is the 10th-warmest and 11th-wettest month of the year here.

Highs ease over the month, from about 14°C in the first days to 11°C by the end. The sky is clear or mostly clear about 25% of the time in December, and the air most often feels dry.

Daylight stretches from about 10 hours at the start of December to 9 h 54 min by month's end. Set against the rest of the year, December is Saikai's 7th-clearest and 2nd-windiest month. For the whole year in context, see Saikai's year-round climate.

Daytime high
12°
10th warmest
Overnight low
3rd coldest
Rainfall
81 mm
9.2 wet days
Daylight
9 h 48 min
7:22 AM – 5:12 PM
Cloud cover
62%
7th clearest
Wind
17 km/h
2nd windiest
Solar energy
2.14 kWh/m²
Travel score
3.3
out of 10

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 14°C in the first days to 11°C by the end.

A typical December day in Saikai reaches about 12°C in the afternoon and slips back to 9°C overnight — a 3°C spread between the day's warmth and the night's chill. On most days the high lands between 8°C and 16°C. Set against its neighbours, December runs about 5°C cooler than November and about 3°C warmer than January.

10°15°20°151015202531
Avg high (°C)Avg low (°C)
11411
21411
31411
41410
51410
61310
71310
81310
91310
10139
11139
12129
13129
14129
15129
16129
17129
18128
19128
20128
21118
22118
23118
24118
25118
26118
27118
28118
29118
30117
31117

How December really feels in Saikai

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

December sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Saikai weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan10° / 709.60.510.12.1
Feb10° / 8590.410.82.4
Mar13° / 13411.1011.73.6
Apr17° / 13°15810.7012.85.3
May21° / 17°17710.4013.76.3
Jun24° / 21°37215.8014.15.7
Jul27° / 25°30616.20145.3
Aug29° / 26°18214.1013.25.2
Sep26° / 23°18811.3012.26.5
Oct22° / 19°1096.7011.27.4
Nov17° / 14°988010.35.8
Dec12° / 819.209.93.3

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 25% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 18% of December, with mostly cloudy or overcast conditions the remaining 57%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15149
25050
35050
44951
54951
64852
74852
84753
94654
104555
114456
124357
134456
144258
154258
164159
174060
184060
193961
203961
213961
223862
233961
243961
254060
264060
274159
284060
294060
304060
313961

Chance of precipitation in December

Any precipitation

Saikai gets around 81 mm of rain over 9.2 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 29% and peaks near 30% on the wettest days.

0%10%20%30%40%151015202531
Rain chance (%)
130
230
330
430
530
630
730
830
930
1030
1129
1229
1329
1429
1529
1629
1729
1829
1929
2029
2129
2229
2329
2429
2529
2629
2728
2828
2928
3027
3127

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 98% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)
19451
29541
39541
49541
59631
69631
79721
89721
99721
109721
119820
129820
139820
149820
159820
169910
179910
189910
199910
209910
219910
229910
239910
249910
259910
269910
279910
289910
299910
309910
319910

Wind in December

Winds average 17 km/h in December.

Across December, daily wind ranges from about 16 km/h on the calmest days to 17 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202531
Wind speed (km/h)Feels
116light breeze
216light breeze
316light breeze
416light breeze
516light breeze
616light breeze
716light breeze
816light breeze
916light breeze
1017light breeze
1117light breeze
1217light breeze
1317light breeze
1417light breeze
1517light breeze
1617light breeze
1717light breeze
1817light breeze
1917light breeze
2017light breeze
2117light breeze
2217light breeze
2317light breeze
2417light breeze
2517light breeze
2617light breeze
2717light breeze
2817light breeze
2917light breeze
3017light breeze
3117light breeze

Sunrise & sunset in December

DaylightNight

Daylight runs from about 10 hours at the start of December to 9 h 54 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 7:12 AM to 7:29 AM, and sunset from 5:10 PM to 5:20 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
110.07:125:10
210.07:125:10
310.07:135:10
49.97:145:10
59.97:155:10
69.97:165:10
79.97:165:11
89.97:175:11
99.97:185:11
109.97:195:11
119.97:195:11
129.97:205:11
139.97:215:12
149.87:215:12
159.87:225:12
169.87:225:12
179.87:235:13
189.87:245:13
199.87:245:14
209.87:255:14
219.87:255:14
229.87:265:15
239.87:265:15
249.87:275:16
259.87:275:16
269.87:275:17
279.87:285:17
289.87:285:18
299.87:285:19
309.87:295:19
319.97:295:20

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 2.14 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 2.14 kWh/m² to a high of 5.41 kWh/m² in May across the year — December's 2.14 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
12.3Moderate
22.3Moderate
32.3Moderate
42.2Moderate
52.2Moderate
62.2Moderate
72.2Moderate
82.2Moderate
92.2Moderate
102.1Moderate
112.1Moderate
122.1Moderate
132.1Moderate
142.1Moderate
152.1Moderate
162.1Moderate
172.1Moderate
182.1Moderate
192.1Moderate
202.1Moderate
212.1Moderate
222.1Moderate
232.1Moderate
242.1Moderate
252.1Moderate
262.2Moderate
272.2Moderate
282.2Moderate
292.2Moderate
302.2Moderate
312.2Moderate
Planning a trip in December

Hazard calendar for Saikai

In seasonPeak

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

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

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

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

Is December a good time to visit Saikai?

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

3.3
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 Saikai.

What to pack for Saikai in December

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

In December, Saikai sees daytime highs around 12°C and nights near 9°C. Worth packing: a warm layer and rain gear. About 9 days see rain.

a warm layerrain gear

Sea temperature near Saikai in December

The nearest coast averages about 19°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 13 km away) is warmest in August at about 27°C and coldest in February near 15°C.

It's comfortable for a long swim from May 27 to Nov 29 — about 6.1 months when the water holds above 20°C.

15°20°25°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan16Cool
Feb15Cool
Mar16Cool
Apr17Cool
May19Cool
Jun22Refreshing
Jul25Warm
Aug27Warm
Sep26Warm
Oct24Refreshing
Nov21Refreshing
Dec19Cool

UV index in Saikai in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 3. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Saikai peaks around July 15 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 3 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highVery highModerateJul 15UV 10Dec 21UV 3
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar6High
Apr7Very high
May8Very high
Jun9Very high
Jul10Extreme
Aug8Very high
Sep9Very high
Oct7High
Nov4Moderate
Dec3Moderate

Air quality in Saikai 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 Saikai is worst in April — around 24 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 11 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateModerateGoodModerateApr 1324 µg/m³Oct 1212 µg/m³
PM2.5 (µg/m³)Level
Jan16Moderate
Feb19Moderate
Mar23Moderate
Apr24Moderate
May21Moderate
Jun17Moderate
Jul12Good
Aug12Moderate
Sep12Good
Oct11Good
Nov14Moderate
Dec13Moderate
Location & terrain

Where is Saikai?

Saikai sits at 33.0°N, 129.7°E, 184 m above sea level, in Japan. The nearest listed city is Sasebo, 21 km away.

Topography around Saikai

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

Within 3 km, the terrain around Saikai has significant variations in elevation — a maximum elevation change of 353 m around an average of 182 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 564 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,455 m.

The land around Saikai is covered by trees (96%) within 3 km, water (55%) and trees (42%) within 16 km, and water (68%) and trees (24%) within 80 km.

3 km
353 m
16 km
564 m
80 km
1,455 m
treesgrasslandcroplandartificial surfaceswater
December weather nearby: Sasebo 21 km · Togitsu 23 km · Ōmura 26 km · Obita 27 km · Arita 30 km · Nagasaki 32 km · Ureshinomachi-shimojuku 33 km · Imarichō-kō 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 Saikai (32.9839°, 129.6809°, elevation 184 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).