Iiyama weather in October

In October, Iiyama sees average daytime highs of 17°C and overnight lows near 8°C, with 161 mm of precipitation across 15.6 wet days and about 11 hours of daylight. It is the 6th-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 20°C in the first days to 15°C by the end. The sky is clear or mostly clear about 22% of the time in October, and the air most often feels dry.

Daylight stretches from about 11 h 36 min at the start of October to 10 h 30 min by month's end. Set against the rest of the year, October is Iiyama's 3rd-clearest and 6th-windiest month. For the whole year in context, see Iiyama's year-round climate.

Daytime high
17°
6th warmest
Overnight low
7th coldest
Precipitation
161 mm
15.6 wet days
Daylight
11 hours
6:00 AM – 5:03 PM
Cloud cover
65%
3rd clearest
Wind
5 km/h
6th windiest
Solar energy
3.1 kWh/m²
Travel score
4.7
out of 10

Iiyama is city in Nagano Prefecture, Japan.

Density
99/km²
people per km²
Founded
1954

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 20°C in the first days to 15°C by the end.

A typical October day in Iiyama reaches about 17°C in the afternoon and slips back to 8°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 13°C and 21°C. Set against its neighbours, October runs about 6°C cooler than September and about 6°C warmer than November.

10°15°20°25°151015202531
Avg high (°C)Avg low (°C)
12012
22012
32011
41911
51911
61911
71911
81910
91910
101810
111810
12189
13189
14189
15179
16178
17178
18178
19178
20168
21167
22167
23167
24167
25156
26156
27156
28156
29156
30145
31145

How October really feels in Iiyama

Once humidity and wind are folded in, October 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

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

Iiyama weather by month

How October compares with the rest of the year at a glance. October is the 6th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -6°14722.823.49.80.0
Feb / -5°12018.918.510.60.0
Mar / -2°13818.614.811.70.6
Apr13° / 11514.63.512.93.4
May19° / 13314.70.113.95.5
Jun23° / 14°17818.1014.55.2
Jul26° / 18°24321.7014.34.7
Aug27° / 19°16919.6013.44.9
Sep23° / 15°18217012.35.4
Oct17° / 16115.60.1114.7
Nov11° / 11616.44.6102.3
Dec / -3°13820.4179.50.2

Cloud cover in October

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 22% of the time in October.

Beyond those clear spells, partly cloudy skies cover about 20% of October, with mostly cloudy or overcast conditions the remaining 58%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13367
23367
33367
43367
53367
63466
73565
83664
93664
103763
113961
124060
134060
144159
154258
164357
174357
184456
194456
204555
214654
224753
234753
244852
254951
264951
275050
285050
295149
305248
315149

Chance of precipitation in October

Any precipitationSnow

Iiyama gets around 161 mm of rain and snow over 15.6 wet days in October. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 49% and peaks near 54% on the wettest days, and about 0 day brings snow.

0%20%40%60%151015202531
Rain chance (%)Snow chance (%)
1540
2540
3530
4530
5530
6530
7520
8520
9520
10510
11510
12500
13490
14480
15480
16470
17470
18470
19470
20470
21471
22471
23471
24471
25471
26481
27482
28482
29482
30482
31483

Humidity in October

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, October lands in the dry band about 85% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)
1603091
2622981
3642871
4662761
5692650
6712540
7722440
8732340
9762130
10772030
11801820
12821620
13831520
14851320
15861220
16891010
1790910
1891810
1992710
2094510
2195410
2296400
2397300
2498200
2598200
2698200
2799100
2899100
2999100
3099100
31100000

Wind in October

Winds average 5 km/h in October.

Across October, daily wind ranges from about 5 km/h on the calmest days to 5 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (km/h)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm
315calm

Sunrise & sunset in October

DaylightNight

Daylight runs from about 11 h 36 min at the start of October to 10 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 66 minutes over October. Sunrise moves from 5:47 AM to 6:15 AM, and sunset from 5:24 PM to 4:45 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
111.65:475:24
211.65:485:23
311.55:485:21
411.55:495:20
511.55:505:18
611.45:515:17
711.45:525:15
811.35:535:14
911.35:545:12
1011.35:555:11
1111.25:565:10
1211.25:575:08
1311.25:585:07
1411.15:585:05
1511.15:595:04
1611.06:005:03
1711.06:015:01
1811.06:025:00
1910.96:034:59
2010.96:044:58
2110.96:054:56
2210.86:064:55
2310.86:074:54
2410.76:084:53
2510.76:094:51
2610.76:104:50
2710.66:114:49
2810.66:124:48
2910.66:134:47
3010.56:144:46
3110.56:154:45

Solar energy in October

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in October, about 3.1 kWh/m².

For context, solar energy here swings from a low near 2.15 kWh/m² to a high of 5.65 kWh/m² in May across the year — October's 3.1 kWh/m² falls in the middle.

01234151015202531
Solar energy (kWh/m²)Level
13.4Moderate
23.4Moderate
33.4Moderate
43.3Moderate
53.3Moderate
63.3Moderate
73.3Moderate
83.3Moderate
93.2Moderate
103.2Moderate
113.2Moderate
123.2Moderate
133.2Moderate
143.2Moderate
153.2Moderate
163.1Moderate
173.1Moderate
183.1Moderate
193.1Moderate
203.1Moderate
213.0Moderate
223.0Moderate
233.0Moderate
243.0Moderate
253.0Moderate
262.9Moderate
272.9Moderate
282.9Moderate
292.9Moderate
302.8Moderate
312.8Moderate
Planning a trip in October

Hazard calendar for Iiyama

In seasonPeak

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

Iiyama 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 Iiyama?

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

4.7
Sightseeing
5th-best month of the year
1.3
Beach & pool
6th-best month of the year

October is a reasonable time to visit Iiyama for sightseeing.

What to pack for Iiyama in October

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

In October, Iiyama sees daytime highs around 17°C and nights near 8°C. Pack rain gear. About 16 days see rain.

rain gear

Sea temperature near Iiyama in October

The nearest coast averages about 22°C in October — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 37 km away) is warmest in August at about 27°C and coldest in March near 10°C.

It's comfortable for a long swim from Jun 20 to Nov 1 — about 4.4 months when the water holds above 20°C.

10°20°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan13Bracing
Feb11Bracing
Mar10Bracing
Apr11Bracing
May15Bracing
Jun20Cool
Jul23Refreshing
Aug27Warm
Sep25Warm
Oct22Refreshing
Nov19Cool
Dec15Cool

UV index in Iiyama 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 Iiyama peaks around August 13 at about 10 (extreme) — 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 highVery highModerateAug 13UV 10Dec 22UV 2
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar5High
Apr7Very high
May9Very high
Jun9Very high
Jul10Very high
Aug10Extreme
Sep9Very high
Oct6High
Nov3Moderate
Dec2Moderate

Air quality in Iiyama 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 Iiyama 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 1721 µg/m³Dec 1510 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar20Moderate
Apr21Moderate
May20Moderate
Jun18Moderate
Jul15Moderate
Aug13Moderate
Sep12Good
Oct11Good
Nov11Good
Dec10Good
Location & terrain

Where is Iiyama?

Iiyama sits at 36.9°N, 138.4°E, 311 m above sea level, in Japan. The nearest listed city is Nakano, 11 km away.

Topography around Iiyama

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

Within 3 km, the terrain around Iiyama has significant variations in elevation — a maximum elevation change of 486 m around an average of 382 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,870 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,978 m.

The land around Iiyama is covered by trees (43%) and cropland (38%) within 3 km, trees (79%) within 16 km, and trees (70%) within 80 km.

3 km
486 m
16 km
1,870 m
80 km
2,978 m
treesgrasslandcroplandartificial surfaceswater
October weather nearby: Nakano 11 km · Arai 21 km · Myoko 22 km · Suzaka 23 km · Nagano 28 km · Jōetsu 35 km · Chikuma 44 km · Sakaki 46 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 Iiyama (36.85°, 138.3667°, elevation 311 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).