Iwamizawa in Summer
In summer (June, July and August), Iwamizawa sees average daytime highs around 23°C and overnight lows near 16°C, with 338 mm of rain over about 34 wet days across the season. It is the warmest season of the year and the wettest season of the year.
Over the season highs climb from about 18°C in early June to 24°C by late August. The sky is clear or mostly clear about 18% of the time across summer, and the air most often feels humid.
Summer is Iwamizawa's best season of the year to visit on our travel score. For the whole year in context, see Iwamizawa's year-round climate.
- Avg daytime high
- 23°C
- warmest season of the year
- Avg overnight low
- 16°C
- Rainfall
- 338 mm
- 34 wet days
- Avg wind
- 10 km/h
- Travel score
- 6.3
- best season of the year
- Months
- Jun · Jul · Aug
Temperature in Iwamizawa in Summer
Over the season highs climb from about 18°C in early June to 24°C by late August.
A typical summer day in Iwamizawa reaches about 23°C and drops to 16°C overnight. The warmest of the three months is August, the coolest June.
How summer really feels in Iwamizawa
Once humidity and wind are folded in, summer brings about 0 days that feel above 32°C and 0 that feel at or below 0°C.
summer sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.
Iwamizawa weather by month
How the three summer months (June, July and August) 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 | -3° / -10° | 49 | 12.7 | 18.1 | 9.2 | 0.0 |
| Feb | -2° / -9° | 42 | 10.7 | 14.9 | 10.2 | 0.0 |
| Mar | 3° / -5° | 57 | 11.6 | 10.5 | 11.6 | 0.1 |
| Apr | 11° / 2° | 67 | 11.8 | 3.3 | 13.1 | 2.5 |
| May | 16° / 8° | 84 | 11.4 | 0.1 | 14.4 | 4.9 |
| Jun | 20° / 12° | 64 | 9.6 | 0 | 15.1 | 6.1 |
| Jul | 23° / 17° | 113 | 11.6 | 0 | 14.9 | 6.4 |
| Aug | 24° / 18° | 161 | 12.5 | 0 | 13.8 | 6.3 |
| Sep | 21° / 13° | 126 | 13.2 | 0 | 12.3 | 5.9 |
| Oct | 15° / 6° | 92 | 13.6 | 0.3 | 10.8 | 4.1 |
| Nov | 7° / 0° | 87 | 16.1 | 8.4 | 9.5 | 0.9 |
| Dec | 0° / -7° | 69 | 15.3 | 18.1 | 8.9 | 0.0 |
Cloud cover in Summer
The sky is clear or mostly clear about 18% of the time across summer.
Chance of precipitation in Summer
Iwamizawa gets around 338 mm of rain over 34 wet days across summer. The line is the day-by-day chance of measurable precipitation.
Humidity in Summer
Most of summer feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Summer
Winds average 10 km/h across summer.
Sunrise & sunset in Summer
Daylight runs from about 14 h 54 min in early June to 13 h 06 min by late August. The lit band spans sunrise to sunset each day.
Solar energy in Summer
Average shortwave solar energy reaching the ground each day across summer, about 4.8 kWh/m².
Hazard calendar for Iwamizawa
In summer, Iwamizawa overlaps its pacific typhoon season. The full year is below, with each hazard's peak months called out.
Iwamizawa sits in the Pacific typhoon belt; the season peaks July–October.
Is summer a good time to visit Iwamizawa?
Our two travel scores rate summer for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
summer is a reasonable time to visit Iwamizawa for sightseeing.
What to pack for Iwamizawa in Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, Iwamizawa sees daytime highs around 23°C and nights near 16°C. Worth packing: light clothes, rain gear and sun protection. About 34 days see rain.
Sea temperature near Iwamizawa in Summer
The nearest coast averages about 18°C across summer — 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 22°C and coldest in February near 5°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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 7 | 5 | 5 | 7 | 10 | 14 | 19 | 22 | 21 | 17 | 13 | 9 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Cool | Refreshing | Refreshing | Cool | Bracing | Bracing |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 7 | Bracing |
| Feb | 5 | Bracing |
| Mar | 5 | Bracing |
| Apr | 7 | Bracing |
| May | 10 | Bracing |
| Jun | 14 | Bracing |
| Jul | 19 | Cool |
| Aug | 22 | Refreshing |
| Sep | 21 | Refreshing |
| Oct | 17 | Cool |
| Nov | 13 | Bracing |
| Dec | 9 | Bracing |
UV index in Iwamizawa in Summer
Clear-sky midday UV across summer averages around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Iwamizawa peaks around August 18 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 1 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 1 | 3 | 3 | 6 | 7 | 7 | 5 | 8 | 6 | 4 | 2 | 1 |
| Level | Low | Moderate | Moderate | High | Very high | High | Moderate | Very high | High | Moderate | Low | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 1 | Low |
| Feb | 3 | Moderate |
| Mar | 3 | Moderate |
| Apr | 6 | High |
| May | 7 | Very high |
| Jun | 7 | High |
| Jul | 5 | Moderate |
| Aug | 8 | Very high |
| Sep | 6 | High |
| Oct | 4 | Moderate |
| Nov | 2 | Low |
| Dec | 1 | Low |
Air quality in Iwamizawa in Summer
Average fine-particle pollution (PM2.5) through the year — so you can see where summer falls, not just the annual average.
Air quality in Iwamizawa 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).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 11 | 15 | 20 | 21 | 19 | 14 | 13 | 11 | 11 | 12 | 10 | 9 |
| Level | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 11 | Good |
| Feb | 15 | Moderate |
| Mar | 20 | Moderate |
| Apr | 21 | Moderate |
| May | 19 | Moderate |
| Jun | 14 | Moderate |
| Jul | 13 | Moderate |
| Aug | 11 | Good |
| Sep | 11 | Good |
| Oct | 12 | Good |
| Nov | 10 | Good |
| Dec | 9 | Good |
Where is Iwamizawa?
Iwamizawa sits at 43.2°N, 141.8°E, 17 m above sea level, in Japan. The nearest listed city is Bibai, 16 km away.
Topography around Iwamizawa
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Iwamizawa.
Within 3 km, the terrain around Iwamizawa has only modest variations in elevation — a maximum elevation change of 101 m around an average of 24 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 559 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,032 m.
The land around Iwamizawa is covered by artificial surfaces (43%) and cropland (35%) within 3 km, cropland (54%) and trees (33%) within 16 km, and trees (64%) 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 Iwamizawa (43.2003°, 141.7597°, elevation 17 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.