Saku weather in January

In January, Saku sees average daytime highs of 3°C and overnight lows near -5°C, with 55 mm of precipitation across 7.5 wet days and about 9.8 hours of daylight. It is the 12th-warmest and 11th-wettest month of the year here.

Day-to-day highs hold fairly steady near 3°C through the month. The sky is clear or mostly clear about 39% of the time in January, and the air most often feels dry.

Daylight stretches from about 9 h 36 min at the start of January to 10 h 12 min by month's end. Set against the rest of the year, January is Saku's 2nd-clearest and 1st-windiest month. For the whole year in context, see Saku's year-round climate.

Daytime high
12th warmest
Overnight low
-5°
2nd coldest
Precipitation
55 mm
7.5 wet days
Daylight
9 h 48 min
7:02 AM – 4:49 PM
Cloud cover
51%
2nd clearest
Wind
7 km/h
1st windiest
Solar energy
2.96 kWh/m²
Travel score
0.0
out of 10

Saku is city in Nagano Prefecture, Japan.

Density
234/km²
people per km²
Founded
2005

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

Temperature in January

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 3°C through the month.

A typical January day in Saku reaches about 3°C in the afternoon and slips back to -5°C overnight — a 8°C spread between the day's warmth and the night's chill. On most days the high lands between -1°C and 7°C. Set against its neighbours, January runs about 3°C cooler than December and about 1°C cooler than February.

-15°-10°-5°10°151015202531
Avg high (°C)Avg low (°C)
13-4
23-4
33-4
43-4
53-4
63-4
73-4
83-5
93-5
103-5
113-5
123-5
133-5
143-5
153-5
162-5
172-5
182-6
192-6
202-6
212-6
222-6
232-6
242-6
252-6
262-6
272-6
282-6
292-6
302-6
312-6

How January really feels in Saku

Once humidity and wind are folded in, January 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 January is cold — wind chill drags the overnight "feels like" below the raw low.

Saku weather by month

How January compares with the rest of the year at a glance. January is the 12th-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -5°557.57.89.80.0
Feb / -5°5787.110.60.0
Mar / -2°9911.77.311.71.3
Apr14° / 10212.32.312.93.9
May19° / 131150.113.95.4
Jun22° / 14°19719.8014.44.8
Jul26° / 18°22021.6014.24.8
Aug27° / 19°17421.6013.44.8
Sep23° / 15°18717.6012.25.3
Oct17° / 16112.9011.15.0
Nov11° / 647.80.610.13.0
Dec / -2°487.95.39.60.4

Cloud cover in January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 39% of the time in January.

Beyond those clear spells, partly cloudy skies cover about 25% of January, with mostly cloudy or overcast conditions the remaining 36%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16931
27030
37030
46931
56931
66931
76832
86832
96733
106634
116634
126535
136535
146436
156436
166238
176238
186238
196139
206040
216040
226040
236040
246040
256139
266139
276139
286139
296238
306238
316238

Chance of precipitation in January

Any precipitationSnow

Saku gets around 55 mm of rain and snow over 7.5 wet days in January. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 25% and peaks near 26% on the wettest days, and about 8 days bring snow.

0%10%20%30%40%151015202531
Rain chance (%)Snow chance (%)
12422
22422
32422
42322
52322
62322
72322
82323
92423
102424
112425
122525
132526
142526
152527
162627
172628
182628
192629
202629
212629
222629
232629
242629
252628
262628
272627
282527
292526
302526
312525

Humidity in January

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, January 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 January

Winds average 7 km/h in January, the windiest month of the year.

Across January, daily wind ranges from about 7 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
17calm
27calm
37calm
47calm
57calm
67calm
77calm
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 January

DaylightNight

Daylight runs from about 9 h 36 min at the start of January to 10 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 36 minutes over January. Sunrise moves from 7:02 AM to 6:55 AM, and sunset from 4:36 PM to 5:04 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.67:024:36
29.67:024:37
39.67:024:38
49.67:024:39
59.67:034:39
69.67:034:40
79.67:034:41
89.77:034:42
99.77:034:43
109.77:034:44
119.77:034:44
129.77:024:45
139.77:024:46
149.77:024:47
159.87:024:48
169.87:024:49
179.87:014:50
189.87:014:51
199.87:014:52
209.97:014:53
219.97:004:54
229.97:004:55
239.96:594:56
2410.06:594:57
2510.06:584:58
2610.06:584:59
2710.06:575:00
2810.16:575:01
2910.16:565:02
3010.16:555:03
3110.26:555:04

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 2.96 kWh/m².

For context, solar energy here swings from a low near 2.52 kWh/m² to a high of 5.67 kWh/m² in May across the year — January's 2.96 kWh/m² sits near the bottom.

01234151015202531
Solar energy (kWh/m²)Level
12.7Moderate
22.8Moderate
32.8Moderate
42.8Moderate
52.8Moderate
62.8Moderate
72.8Moderate
82.8Moderate
92.8Moderate
102.8Moderate
112.8Moderate
122.8Moderate
132.8Moderate
142.8Moderate
152.9Moderate
162.9Moderate
172.9Moderate
182.9Moderate
193.0Moderate
203.0Moderate
213.0Moderate
223.0Moderate
233.1Moderate
243.1Moderate
253.1Moderate
263.2Moderate
273.2Moderate
283.2Moderate
293.3Moderate
303.3Moderate
313.4Moderate
Planning a trip in January

Hazard calendar for Saku

In seasonPeak

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

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

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

Is January a good time to visit Saku?

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

0.0
Sightseeing
11th-best month of the year
0.0
Beach & pool
9th-best month of the year

January is a weaker month for outdoor sightseeing in Saku.

What to pack for Saku in January

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

In January, Saku sees daytime highs around 3°C and nights near -5°C. Pack a warm layer and a heavy coat. About 8 days see rain.

a warm layera heavy coat

UV index in Saku in January

LowModerateHighVery highExtreme

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

Under clear skies, the midday UV index in Saku peaks around July 18 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 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 22UV 2
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar5High
Apr7Very high
May9Very high
Jun10Very high
Jul10Very high
Aug10Very high
Sep9Very high
Oct6High
Nov3Moderate
Dec2Moderate

Air quality in Saku in January

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Saku 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 Saku?

Saku sits at 36.2°N, 138.5°E, 684 m above sea level, in Japan. The nearest listed city is Komoro, 12 km away.

Topography around Saku

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

Within 3 km, the terrain around Saku has significant variations in elevation — a maximum elevation change of 321 m around an average of 712 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,343 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,145 m.

The land around Saku is covered by cropland (35%), artificial surfaces (32%) and trees (23%) within 3 km, trees (72%) within 16 km, and trees (81%) within 80 km.

3 km
321 m
16 km
1,343 m
80 km
3,145 m
treesgrasslandcroplandartificial surfacesbare terrainwater
January weather nearby: Komoro 12 km · Miyota 14 km · Tōmi 19 km · Karuizawa 20 km · Kamimaruko 22 km · Ueda 27 km · Tomioka 37 km · Chino 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 Saku (36.2167°, 138.4833°, elevation 684 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).