Iruma in Fall
In fall (September, October and November), Iruma sees average daytime highs around 19°C and overnight lows near 12°C, with 592 mm of precipitation over about 46 wet days across the season. It is the 2nd-warmest season and the 2nd-wettest season.
Over the season highs ease from about 27°C in early September to 12°C by late November. The sky is clear or mostly clear about 29% of the time across fall, and the air most often feels dry.
Fall is Iruma's best season of the year to visit on our travel score. For the whole year in context, see Iruma's year-round climate.
- Avg daytime high
- 19°C
- 2nd-warmest season
- Avg overnight low
- 12°C
- Precipitation
- 592 mm
- 46 wet days
- Avg wind
- 6 km/h
- Travel score
- 4.8
- best season of the year
- Months
- Sep · Oct · Nov
Temperature in Iruma in Fall
Over the season highs ease from about 27°C in early September to 12°C by late November.
A typical fall day in Iruma reaches about 19°C and drops to 12°C overnight. The warmest of the three months is September, the coolest November.
How fall really feels in Iruma
Once humidity and wind are folded in, fall brings about 0 days that feel above 32°C and 0 that feel at or below 0°C.
fall sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.
Iruma weather by month
How the three fall months (September, October and November) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 7° / -2° | 77 | 8.5 | 4.4 | 9.8 | 1.0 |
| Feb | 8° / -1° | 75 | 9.6 | 4.6 | 10.6 | 1.2 |
| Mar | 11° / 2° | 139 | 15.2 | 4.7 | 11.7 | 2.5 |
| Apr | 16° / 7° | 146 | 14.6 | 0.9 | 12.9 | 4.5 |
| May | 21° / 13° | 166 | 15.6 | 0 | 13.9 | 5.5 |
| Jun | 23° / 17° | 222 | 19.5 | 0 | 14.4 | 4.9 |
| Jul | 27° / 21° | 243 | 21.8 | 0 | 14.2 | 4.5 |
| Aug | 28° / 22° | 205 | 21 | 0 | 13.4 | 4.4 |
| Sep | 25° / 18° | 249 | 18.3 | 0 | 12.2 | 5.2 |
| Oct | 19° / 13° | 242 | 16.2 | 0 | 11.1 | 5.2 |
| Nov | 14° / 7° | 101 | 11.3 | 0.2 | 10.1 | 4.1 |
| Dec | 10° / 1° | 68 | 8.3 | 1.4 | 9.6 | 2.2 |
Cloud cover in Fall
The sky is clear or mostly clear about 29% of the time across fall.
Chance of precipitation in Fall
Iruma gets around 592 mm of rain and snow over 46 wet days across fall. The line is the day-by-day chance of measurable precipitation.
Humidity in Fall
Most of fall feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Fall
Winds average 6 km/h across fall.
Sunrise & sunset in Fall
Daylight runs from about 12 h 48 min in early September to 9 h 48 min by late November. The lit band spans sunrise to sunset each day.
Solar energy in Fall
Average shortwave solar energy reaching the ground each day across fall, about 3.0 kWh/m².
Hazard calendar for Iruma
In fall, Iruma overlaps its pacific typhoon season. The full year is below, with each hazard's peak months called out.
Iruma sits in the Pacific typhoon belt; the season peaks July–October.
Is fall a good time to visit Iruma?
Our two travel scores rate fall for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
fall is a reasonable time to visit Iruma for sightseeing.
What to pack for Iruma in Fall
From fall's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In fall, Iruma sees daytime highs around 19°C and nights near 12°C. Pack rain gear. Worth having: light clothes and a warm layer. About 46 days see rain.
Sea temperature near Iruma in Fall
The nearest coast averages about 22°C across fall — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 51 km away) is warmest in August at about 26°C and coldest in February near 13°C.
It's comfortable for a long swim from Jun 7 to Nov 3 — about 4.9 months when the water holds above 20°C.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 14 | 13 | 13 | 15 | 18 | 21 | 23 | 26 | 25 | 22 | 19 | 16 |
| Comfort | Bracing | Bracing | Bracing | Cool | Cool | Refreshing | Refreshing | Warm | Warm | Refreshing | Cool | Cool |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 14 | Bracing |
| Feb | 13 | Bracing |
| Mar | 13 | Bracing |
| Apr | 15 | Cool |
| May | 18 | Cool |
| Jun | 21 | Refreshing |
| Jul | 23 | Refreshing |
| Aug | 26 | Warm |
| Sep | 25 | Warm |
| Oct | 22 | Refreshing |
| Nov | 19 | Cool |
| Dec | 16 | Cool |
UV index in Iruma in Fall
Clear-sky midday UV across fall averages 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 Iruma peaks around July 15 at about 10 (very high) — 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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 4 | 4 | 7 | 8 | 9 | 10 | 9 | 8 | 6 | 3 | 2 |
| Level | Moderate | Moderate | Moderate | High | Very high | Very high | Very high | Very high | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Moderate |
| Feb | 4 | Moderate |
| Mar | 4 | Moderate |
| Apr | 7 | High |
| May | 8 | Very high |
| Jun | 9 | Very high |
| Jul | 10 | Very high |
| Aug | 9 | Very high |
| Sep | 8 | Very high |
| Oct | 6 | High |
| Nov | 3 | Moderate |
| Dec | 2 | Moderate |
Air quality in Iruma in Fall
Average fine-particle pollution (PM2.5) through the year — so you can see where fall falls, not just the annual average.
Air quality in Iruma is worst in April — around 26 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (December, 14 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 15 | 21 | 25 | 26 | 24 | 20 | 17 | 16 | 16 | 16 | 16 | 14 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 15 | Moderate |
| Feb | 21 | Moderate |
| Mar | 25 | Moderate |
| Apr | 26 | Moderate |
| May | 24 | Moderate |
| Jun | 20 | Moderate |
| Jul | 17 | Moderate |
| Aug | 16 | Moderate |
| Sep | 16 | Moderate |
| Oct | 16 | Moderate |
| Nov | 16 | Moderate |
| Dec | 14 | Moderate |
Where is Iruma?
Iruma sits at 35.8°N, 139.4°E, 126 m above sea level, in Japan. The nearest listed city is Sayama, 6.0 km away.
Topography around Iruma
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Iruma.
Within 3 km, the terrain around Iruma has only modest variations in elevation — a maximum elevation change of 140 m around an average of 124 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 725 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,737 m.
The land around Iruma is covered by artificial surfaces (53%) and trees (36%) within 3 km, artificial surfaces (49%) and trees (39%) within 16 km, and trees (46%) and artificial surfaces (28%) within 80 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
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 Iruma (35.818°, 139.368°, elevation 126 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.