Otaru weather in September

In September, Otaru sees average daytime highs of 20°C and overnight lows near 16°C, with 149 mm of rain across 13.9 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 2nd-wettest month of the year here.

Highs ease over the month, from about 22°C in the first days to 17°C by the end. The sky is clear or mostly clear about 27% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Otaru's 4th-clearest and 8th-windiest month. For the whole year in context, see Otaru's year-round climate.

Daytime high
20°
3rd warmest
Overnight low
16°
10th coldest
Rainfall
149 mm
13.9 wet days
Daylight
12 h 18 min
5:22 AM – 5:39 PM
Cloud cover
63%
4th clearest
Wind
12 km/h
8th windiest
Solar energy
3.83 kWh/m²
Travel score
5.6
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 22°C in the first days to 17°C by the end.

A typical September day in Otaru reaches about 20°C in the afternoon and slips back to 16°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 17°C and 23°C. Set against its neighbours, September runs about 3°C cooler than August and about 6°C warmer than October.

10°15°20°25°151015202530
Avg high (°C)Avg low (°C)
12218
22218
32218
42218
52118
62117
72117
82117
92117
102117
112117
122016
132016
142016
152016
162016
172015
181915
191915
201915
211915
221914
231814
241814
251814
261814
271813
281713
291713
301713

How September really feels in Otaru

Once humidity and wind are folded in, September 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

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

Otaru weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 2nd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-3° / -6°9820.824.29.20.0
Feb-2° / -6°791820.210.20.0
Mar / -3°761515.411.60.0
Apr / 6611.2513.10.7
May12° / 8411.70.414.43.0
Jun17° / 12°7610.6015.15.1
Jul21° / 17°12712.8014.95.9
Aug23° / 19°16314.2013.86.0
Sep20° / 16°14913.9012.35.6
Oct14° / 11714.90.610.83.5
Nov / 12918.611.29.50.7
Dec-0° / -3°12621.922.58.90.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 27% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 56%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14159
24159
34159
44258
54159
64159
74159
84159
94159
104357
114456
124456
134456
144456
154456
164654
174654
184654
194654
204654
214753
224753
234753
244654
254654
264654
274654
284654
294555
304654

Chance of precipitation in September

Any precipitation

Otaru gets around 149 mm of rain over 13.9 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 47% and peaks near 51% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
145
245
345
445
545
645
745
845
945
1045
1145
1245
1345
1445
1545
1646
1746
1846
1946
2047
2147
2248
2349
2449
2550
2650
2751
2851
2951
3051

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 37% of days. Sticky, muggy-or-worse air turns up on roughly 10% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
172838243
282837233
392937223
4113037203
5123136192
6143135182
7153234162
8173333152
9193332142
10213430132
11243429112
12263527102
1329352691
1432352481
1535352271
1638352061
1741351861
1843351651
1946351441
2049351240
2152351030
225434930
235634820
245933620
256232510
266431410
276530410
286729310
297027300
307226200

Wind in September

Winds average 12 km/h in September.

Across September, daily wind ranges from about 11 km/h on the calmest days to 14 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
111calm
211calm
311calm
411calm
511calm
611calm
711calm
811calm
912calm
1012calm
1112calm
1212calm
1312calm
1412light breeze
1512light breeze
1612light breeze
1712light breeze
1812light breeze
1913light breeze
2013light breeze
2113light breeze
2213light breeze
2313light breeze
2413light breeze
2513light breeze
2614light breeze
2714light breeze
2814light breeze
2914light breeze
3014light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 84 minutes over September. Sunrise moves from 5:05 AM to 5:38 AM, and sunset from 6:07 PM to 5:13 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:056:07
213.05:066:05
312.95:076:03
412.95:086:01
512.85:096:00
612.85:105:58
712.75:115:56
812.75:135:54
912.65:145:52
1012.65:155:50
1112.55:165:48
1212.55:175:47
1312.45:185:45
1412.45:195:43
1512.35:205:41
1612.35:225:39
1712.25:235:37
1812.25:245:35
1912.15:255:33
2012.15:265:31
2112.05:275:30
2212.05:285:28
2311.95:305:26
2411.95:315:24
2511.85:325:22
2611.85:335:20
2711.75:345:18
2811.75:355:17
2911.65:375:15
3011.65:385:13

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 3.83 kWh/m².

For context, solar energy here swings from a low near 1.4 kWh/m² to a high of 5.59 kWh/m² in May across the year — September's 3.83 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.2Bright
24.2Bright
34.2Bright
44.1Bright
54.1Bright
64.1Bright
74.0Bright
84.0Bright
94.0Moderate
104.0Moderate
113.9Moderate
123.9Moderate
133.9Moderate
143.9Moderate
153.8Moderate
163.8Moderate
173.8Moderate
183.8Moderate
193.7Moderate
203.7Moderate
213.7Moderate
223.6Moderate
233.6Moderate
243.6Moderate
253.5Moderate
263.5Moderate
273.5Moderate
283.4Moderate
293.4Moderate
303.4Moderate
Planning a trip in September

Hazard calendar for Otaru

In seasonPeak

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

Otaru 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 September a good time to visit Otaru?

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

5.6
Sightseeing
3rd-best month of the year
2.7
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Otaru for sightseeing.

What to pack for Otaru in September

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

In September, Otaru sees daytime highs around 20°C and nights near 16°C. Pack rain gear. About 14 days see rain.

rain gear

Sea temperature near Otaru in September

The nearest coast averages about 21°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 23 km away) is warmest in August at about 22°C and coldest in February near 6°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
Feb6Bracing
Mar6Bracing
Apr7Bracing
May10Bracing
Jun14Bracing
Jul19Cool
Aug22Refreshing
Sep21Refreshing
Oct17Cool
Nov13Bracing
Dec9Bracing

UV index in Otaru in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Otaru peaks around August 18 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 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 22UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar3Moderate
Apr5High
May7Very high
Jun7High
Jul5Moderate
Aug8Very high
Sep6High
Oct4Moderate
Nov2Low
Dec1Low

Air quality in Otaru in September

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Otaru 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 1121 µg/m³Dec 169 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb15Moderate
Mar21Moderate
Apr21Moderate
May19Moderate
Jun13Moderate
Jul12Moderate
Aug11Good
Sep10Good
Oct12Good
Nov11Good
Dec9Good
Location & terrain

Where is Otaru?

Otaru sits at 43.2°N, 141.0°E, 30 m above sea level, in Japan. The nearest listed city is Yoichi, 19 km away.

Topography around Otaru

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

Within 3 km, the terrain around Otaru has significant variations in elevation — a maximum elevation change of 508 m around an average of 83 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,289 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,867 m.

The land around Otaru is covered by trees (44%), artificial surfaces (32%) and water (23%) within 3 km, water (49%) and trees (46%) within 16 km, and trees (48%) and water (37%) within 80 km.

3 km
508 m
16 km
1,289 m
80 km
1,867 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Yoichi 19 km · Ishikari 29 km · Sapporo 31 km · Kutchan 38 km · Tōbetsu 42 km · Ebetsu 45 km · Niseko 50 km · Kitahiroshima 52 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 Otaru (43.1894°, 141.0022°, elevation 30 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).