Iwase in Summer
In summer (June, July and August), Iwase sees average daytime highs around 29°C and overnight lows near 21°C, with 435 mm of rain over about 44 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 25°C in early June to 30°C by late August. The sky is clear or mostly clear about 14% of the time across summer, and the air most often feels oppressive.
Summer is Iwase's 3rd-best season to visit on our travel score. For the whole year in context, see Iwase's year-round climate.
- Avg daytime high
- 29°C
- warmest season of the year
- Avg overnight low
- 21°C
- Rainfall
- 435 mm
- 44 wet days
- Avg wind
- 8 km/h
- Travel score
- 4.7
- 3rd-best season
- Months
- Jun · Jul · Aug
Temperature in Iwase in Summer
Over the season highs climb from about 25°C in early June to 30°C by late August.
A typical summer day in Iwase reaches about 29°C and drops to 21°C overnight. The warmest of the three months is August, the coolest June.
How summer really feels in Iwase
Once humidity and wind are folded in, summer brings about 48 days that feel above 32°C and 0 that feel at or below 0°C.
The story in summer is heat — humidity pushes the afternoon "feels like" well above the raw temperature.
Iwase 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 | 9° / -0° | 55 | 6.1 | 1.3 | 9.8 | 1.9 |
| Feb | 10° / 1° | 54 | 6.7 | 1.8 | 10.6 | 2.3 |
| Mar | 13° / 3° | 100 | 11.5 | 0.8 | 11.7 | 3.7 |
| Apr | 18° / 9° | 107 | 11.1 | 0.1 | 12.9 | 5.6 |
| May | 23° / 14° | 134 | 12.5 | 0 | 13.9 | 6.3 |
| Jun | 26° / 18° | 147 | 14.6 | 0 | 14.4 | 5.5 |
| Jul | 30° / 22° | 165 | 15.9 | 0 | 14.2 | 4.4 |
| Aug | 31° / 23° | 123 | 13.7 | 0 | 13.4 | 4.1 |
| Sep | 27° / 20° | 164 | 14.2 | 0 | 12.2 | 5.5 |
| Oct | 21° / 14° | 176 | 12.3 | 0 | 11.1 | 6.2 |
| Nov | 16° / 7° | 80 | 8.7 | 0 | 10.1 | 5.2 |
| Dec | 11° / 2° | 52 | 6.5 | 0.2 | 9.6 | 3.1 |
Cloud cover in Summer
The sky is clear or mostly clear about 14% of the time across summer.
Chance of precipitation in Summer
Iwase gets around 435 mm of rain over 44 wet days across summer. The line is the day-by-day chance of measurable precipitation.
Humidity in Summer
Most of summer feels oppressive — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Summer
Winds average 8 km/h across summer.
Sunrise & sunset in Summer
Daylight runs from about 14 h 18 min in early June to 12 h 48 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 4.5 kWh/m².
Hazard calendar for Iwase
In summer, Iwase overlaps its pacific typhoon season. The full year is below, with each hazard's peak months called out.
Iwase sits in the Pacific typhoon belt; the season peaks July–October.
Is summer a good time to visit Iwase?
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 Iwase for sightseeing.
What to pack for Iwase in Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, Iwase sees daytime highs around 29°C and nights near 21°C. Pack light clothes and rain gear. Worth having: sun protection. About 44 days see rain.
Sea temperature near Iwase in Summer
The nearest coast averages about 22°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 47 km away) is warmest in August at about 24°C and coldest in February near 13°C.
It's comfortable for a long swim from Jun 24 to Oct 28 — about 4.2 months when the water holds above 20°C.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 15 | 13 | 13 | 15 | 17 | 19 | 22 | 24 | 23 | 21 | 19 | 16 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Cool | Cool | Refreshing | Warm | Refreshing | Refreshing | Cool | Cool |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 15 | Bracing |
| Feb | 13 | Bracing |
| Mar | 13 | Bracing |
| Apr | 15 | Bracing |
| May | 17 | Cool |
| Jun | 19 | Cool |
| Jul | 22 | Refreshing |
| Aug | 24 | Warm |
| Sep | 23 | Refreshing |
| Oct | 21 | Refreshing |
| Nov | 19 | Cool |
| Dec | 16 | Cool |
UV index in Iwase in Summer
Clear-sky midday UV across summer averages around 9 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Iwase peaks around July 17 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 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 | 6 | 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 | 6 | 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 Iwase 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 Iwase is worst in March — around 25 µg/m³ PM2.5 (moderate), about 1.8× 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 | 18 | 25 | 25 | 24 | 19 | 16 | 15 | 15 | 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 | 18 | Moderate |
| Mar | 25 | Moderate |
| Apr | 25 | Moderate |
| May | 24 | Moderate |
| Jun | 19 | Moderate |
| Jul | 16 | Moderate |
| Aug | 15 | Moderate |
| Sep | 15 | Moderate |
| Oct | 16 | Moderate |
| Nov | 16 | Moderate |
| Dec | 14 | Moderate |
Where is Iwase?
Iwase sits at 36.4°N, 140.1°E, 49 m above sea level, in Japan. The nearest listed city is Makabe, 9.0 km away.
Topography around Iwase
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Iwase.
Within 3 km, the terrain around Iwase has significant variations in elevation — a maximum elevation change of 367 m around an average of 82 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 850 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,458 m.
The land around Iwase is covered by trees (48%) and cropland (33%) within 3 km, trees (50%) and cropland (32%) within 16 km, and trees (43%), cropland (21%) and artificial surfaces (20%) 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 Iwase (36.35°, 140.1°, elevation 49 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.