Isumi weather in October

In October, Isumi sees average daytime highs of 21°C and overnight lows near 19°C, with 239 mm of rain across 14.9 wet days and about 11.1 hours of daylight. It is the 5th-warmest and 1st-wettest month of the year here.

Highs ease over the month, from about 23°C in the first days to 20°C by the end. The sky is clear or mostly clear about 30% of the time in October, and the air most often feels comfortable.

Daylight stretches from about 11 h 36 min at the start of October to 10 h 36 min by month's end. Set against the rest of the year, October is Isumi's 8th-clearest and 6th-windiest month. For the whole year in context, see Isumi's year-round climate.

Daytime high
21°
5th warmest
Overnight low
19°
8th coldest
Rainfall
239 mm
14.9 wet days
Daylight
11 h 06 min
5:51 AM – 4:56 PM
Cloud cover
62%
8th clearest
Wind
19 km/h
6th windiest
Solar energy
3.09 kWh/m²
Travel score
5.8
out of 10

Isumi is city in Chiba Prefecture, Japan.

Density
226/km²
people per km²
Founded
2005

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

Temperature in October

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 23°C in the first days to 20°C by the end.

A typical October day in Isumi reaches about 21°C in the afternoon and slips back to 19°C overnight — a 3°C spread between the day's warmth and the night's chill. On most days the high lands between 19°C and 24°C. Set against its neighbours, October runs about 4°C cooler than September and about 4°C warmer than November.

10°15°20°25°30°151015202531
Avg high (°C)Avg low (°C)
12321
22321
32321
42320
52320
62320
72320
82220
92220
102220
112219
122219
132219
142219
152219
162119
172119
182118
192118
202118
212118
222118
232018
242017
252017
262017
272017
282017
292017
302017
311916

Isumi weather by month

How October compares with the rest of the year at a glance. October is the 5th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan10° / 10810.79.92.5
Feb11° / 10110.610.72.4
Mar13° / 15914.611.73.2
Apr16° / 13°12612.612.94.8
May20° / 17°13811.813.85.9
Jun23° / 20°19013.514.35.8
Jul26° / 24°13311.814.16.2
Aug28° / 25°1001113.36.2
Sep25° / 23°18814.712.25.9
Oct21° / 19°23914.911.15.8
Nov17° / 14°14713.410.15.2
Dec13° / 10611.79.73.6

Cloud cover in October

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 30% of the time in October.

Beyond those clear spells, partly cloudy skies cover about 14% of October, with mostly cloudy or overcast conditions the remaining 56%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13664
23763
33763
43862
53862
64060
74060
84060
94159
104159
114159
124159
134258
144258
154357
164456
174555
184555
194555
204753
214654
224753
234753
244852
254951
264951
275050
285050
295149
305149
315248

Chance of precipitation in October

Any precipitation

Isumi gets around 239 mm of rain over 14.9 wet days in October, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 48% and peaks near 50% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202531
Rain chance (%)
150
250
350
450
550
650
750
850
950
1050
1150
1250
1349
1449
1549
1648
1748
1847
1947
2047
2147
2246
2346
2445
2545
2645
2744
2844
2943
3043
3143

Humidity in October

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, October lands in the comfortable band about 32% of days. Sticky, muggy-or-worse air turns up on roughly 20% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
17172935121
28182934111
38192934100
4920303390
51021303280
61022293170
71123293070
81225292860
91326292660
101328292550
111430282350
121532282140
131633281940
141835271730
151936271530
162037261430
172138261230
182339251120
19254025920
20264024820
21284024710
22304023610
23323923510
24343922410
25363822400
26383721300
27403620300
28423620300
29443519200
30463418200
31483318200

Wind in October

Winds average 19 km/h in October.

Across October, daily wind ranges from about 18 km/h on the calmest days to 20 km/h at its breeziest. It stays fairly steady from day to day.

0510152025151015202531
Wind speed (km/h)Feels
119light breeze
219light breeze
320light breeze
420light breeze
520light breeze
620light breeze
720light breeze
820light breeze
920light breeze
1020light breeze
1119light breeze
1219light breeze
1319light breeze
1419light breeze
1519light breeze
1619light breeze
1719light breeze
1819light breeze
1919light breeze
2019light breeze
2119light breeze
2219light breeze
2319light breeze
2419light breeze
2518light breeze
2618light breeze
2718light breeze
2818light breeze
2918light breeze
3018light breeze
3118light breeze

Sunrise & sunset in October

DaylightNight

Daylight runs from about 11 h 36 min at the start of October to 10 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 60 minutes over October. Sunrise moves from 5:38 AM to 6:05 AM, and sunset from 5:17 PM to 4:39 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
111.65:385:17
211.65:395:15
311.65:405:14
411.55:405:13
511.55:415:11
611.55:425:10
711.45:435:08
811.45:445:07
911.45:445:06
1011.35:455:04
1111.35:465:03
1211.25:475:01
1311.25:485:00
1411.25:494:59
1511.15:504:58
1611.15:514:56
1711.15:514:55
1811.05:524:54
1911.05:534:53
2011.05:544:51
2110.95:554:50
2210.95:564:49
2310.85:574:48
2410.85:584:47
2510.85:594:46
2610.76:004:44
2710.76:014:43
2810.76:024:42
2910.66:034:41
3010.66:044:40
3110.66:054:39

Solar energy in October

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in October, about 3.09 kWh/m².

For context, solar energy here swings from a low near 2.25 kWh/m² to a high of 5.53 kWh/m² in August across the year — October's 3.09 kWh/m² falls in the middle.

01234151015202531
Solar energy (kWh/m²)Level
13.5Moderate
23.4Moderate
33.4Moderate
43.4Moderate
53.3Moderate
63.3Moderate
73.3Moderate
83.3Moderate
93.2Moderate
103.2Moderate
113.2Moderate
123.2Moderate
133.1Moderate
143.1Moderate
153.1Moderate
163.1Moderate
173.1Moderate
183.0Moderate
193.0Moderate
203.0Moderate
213.0Moderate
223.0Moderate
233.0Moderate
243.0Moderate
252.9Moderate
262.9Moderate
272.9Moderate
282.9Moderate
292.9Moderate
302.8Moderate
312.8Moderate
Planning a trip in October

Hazard calendar for Isumi

In seasonPeak

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

Isumi 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 October a good time to visit Isumi?

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

5.8
Sightseeing
5th-best month of the year
3.8
Beach & pool
5th-best month of the year

October is a reasonable time to visit Isumi for sightseeing.

What to pack for Isumi in October

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

In October, Isumi sees daytime highs around 21°C and nights near 19°C. Pack rain gear. About 15 days see rain.

rain gear

Sea temperature near Isumi in October

The nearest coast averages about 24°C in October — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in August at about 26°C and coldest in February near 16°C.

It's comfortable for a long swim from May 22 to Dec 9 — about 6.6 months when the water holds above 20°C.

15°20°25°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan18Cool
Feb16Cool
Mar16Cool
Apr18Cool
May20Cool
Jun22Refreshing
Jul24Refreshing
Aug26Warm
Sep26Warm
Oct24Refreshing
Nov22Refreshing
Dec20Cool

UV index in Isumi in October

LowModerateHighVery highExtreme

Clear-sky midday UV in October 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 Isumi peaks around August 11 at about 10 (extreme) — 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 highExtremeVery highHighModerateAug 11UV 10Dec 23UV 2
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar5Moderate
Apr7High
May9Very high
Jun9Very high
Jul10Extreme
Aug10Extreme
Sep8Very high
Oct6High
Nov4Moderate
Dec2Moderate

Air quality in Isumi in October

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Isumi is worst in April — around 22 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (September, 11 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateApr 1322 µg/m³Sep 911 µg/m³
PM2.5 (µg/m³)Level
Jan14Moderate
Feb17Moderate
Mar21Moderate
Apr22Moderate
May21Moderate
Jun16Moderate
Jul12Good
Aug11Good
Sep11Good
Oct14Moderate
Nov14Moderate
Dec13Moderate
Location & terrain

Where is Isumi?

Isumi sits at 35.2°N, 140.4°E, 1 m above sea level, in Japan. The nearest listed city is Ōhara, 2.0 km away.

Topography around Isumi

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

Within 3 km, the terrain around Isumi has only modest variations in elevation — a maximum elevation change of 86 m around an average of 12 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 229 m; within 80 km, significant variations in elevation — a maximum elevation change of 396 m.

The land around Isumi is covered by water (59%) and trees (27%) within 3 km, water (62%) and trees (27%) within 16 km, and water (55%) and trees (21%) within 80 km.

3 km
86 m
16 km
229 m
80 km
396 m
treesgrasslandcroplandartificial surfaceswater
October weather nearby: Ōhara 2.0 km · Katsuura 12 km · Mobara 24 km · Kamogawa 31 km · Ōamishirasato 32 km · Ōami 33 km · Tōgane 36 km · Sodegaura 40 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 Isumi (35.23°, 140.4049°, elevation 1 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).