Iyo in Summer
In summer (June, July and August), Iyo sees average daytime highs around 28°C and overnight lows near 22°C, with 663 mm of rain over about 48 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 24°C in early June to 29°C by late August. The sky is clear or mostly clear about 21% of the time across summer, and the air most often feels oppressive.
Summer is Iyo's 3rd-best season to visit on our travel score. For the whole year in context, see Iyo's year-round climate.
- Avg daytime high
- 28°C
- warmest season of the year
- Avg overnight low
- 22°C
- Rainfall
- 663 mm
- 48 wet days
- Avg wind
- 7 km/h
- Travel score
- 4.9
- 3rd-best season
- Months
- Jun · Jul · Aug
Temperature in Iyo in Summer
Over the season highs climb from about 24°C in early June to 29°C by late August.
A typical summer day in Iyo reaches about 28°C and drops to 22°C overnight. The warmest of the three months is August, the coolest June.
How summer really feels in Iyo
Once humidity and wind are folded in, summer brings about 38 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.
Iyo 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 | 8° / 2° | 69 | 11.3 | 3.3 | 10 | 1.4 |
| Feb | 9° / 3° | 79 | 10.4 | 2.9 | 10.7 | 1.8 |
| Mar | 13° / 5° | 118 | 12.3 | 0.7 | 11.7 | 3.4 |
| Apr | 18° / 10° | 133 | 11 | 0.1 | 12.8 | 5.5 |
| May | 22° / 15° | 154 | 11.1 | 0 | 13.7 | 6.4 |
| Jun | 25° / 19° | 268 | 15.7 | 0 | 14.2 | 5.6 |
| Jul | 29° / 23° | 239 | 16.8 | 0 | 14 | 4.7 |
| Aug | 30° / 24° | 156 | 15.8 | 0 | 13.3 | 4.5 |
| Sep | 27° / 20° | 187 | 13.6 | 0 | 12.2 | 5.9 |
| Oct | 22° / 15° | 141 | 9.4 | 0 | 11.2 | 6.9 |
| Nov | 16° / 9° | 83 | 9.1 | 0 | 10.2 | 5.3 |
| Dec | 11° / 4° | 83 | 11.4 | 1.9 | 9.8 | 2.6 |
Cloud cover in Summer
The sky is clear or mostly clear about 21% of the time across summer.
Chance of precipitation in Summer
Iyo gets around 663 mm of rain over 48 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 7 km/h across summer.
Sunrise & sunset in Summer
Daylight runs from about 14 h 06 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 5.1 kWh/m².
Hazard calendar for Iyo
In summer, Iyo overlaps its pacific typhoon season. The full year is below, with each hazard's peak months called out.
Iyo sits in the Pacific typhoon belt; the season peaks July–October.
Is summer a good time to visit Iyo?
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 Iyo for sightseeing.
What to pack for Iyo in Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, Iyo sees daytime highs around 28°C and nights near 22°C. Pack light clothes and rain gear. Worth having: sun protection. About 48 days see rain.
Sea temperature near Iyo in Summer
The nearest coast averages about 24°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 15 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 12 to Nov 17 — about 5.2 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 | 21 | 24 | 26 | 25 | 23 | 20 | 17 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Cool | Refreshing | Warm | Warm | Warm | Refreshing | Refreshing | Cool |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 15 | Bracing |
| Feb | 13 | Bracing |
| Mar | 13 | Bracing |
| Apr | 15 | Bracing |
| May | 17 | Cool |
| Jun | 21 | Refreshing |
| Jul | 24 | Warm |
| Aug | 26 | Warm |
| Sep | 25 | Warm |
| Oct | 23 | Refreshing |
| Nov | 20 | Refreshing |
| Dec | 17 | Cool |
UV index in Iyo in Summer
Clear-sky midday UV across summer averages around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Iyo peaks around June 23 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 3 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 3 | 5 | 6 | 7 | 9 | 10 | 10 | 9 | 10 | 7 | 4 | 3 |
| Level | Moderate | Moderate | High | Very high | Very high | Extreme | Extreme | Very high | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 3 | Moderate |
| Feb | 5 | Moderate |
| Mar | 6 | High |
| Apr | 7 | Very high |
| May | 9 | Very high |
| Jun | 10 | Extreme |
| Jul | 10 | Extreme |
| Aug | 9 | Very high |
| Sep | 10 | Very high |
| Oct | 7 | High |
| Nov | 4 | Moderate |
| Dec | 3 | Moderate |
Air quality in Iyo 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 Iyo is worst in April — around 23 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 11 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) | 14 | 17 | 21 | 23 | 21 | 19 | 15 | 15 | 12 | 11 | 12 | 11 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 14 | Moderate |
| Feb | 17 | Moderate |
| Mar | 21 | Moderate |
| Apr | 23 | Moderate |
| May | 21 | Moderate |
| Jun | 19 | Moderate |
| Jul | 15 | Moderate |
| Aug | 15 | Moderate |
| Sep | 12 | Moderate |
| Oct | 11 | Good |
| Nov | 12 | Good |
| Dec | 11 | Good |
Where is Iyo?
Iyo sits at 33.8°N, 132.7°E, 14 m above sea level, in Japan. The nearest listed city is Masaki-chō, 4.0 km away.
Topography around Iyo
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Iyo.
Within 3 km, the terrain around Iyo has significant variations in elevation — a maximum elevation change of 427 m around an average of 50 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 1,141 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,895 m.
The land around Iyo is covered by trees (30%), water (29%) and artificial surfaces (24%) within 3 km, trees (44%) and water (37%) within 16 km, and trees (52%) and water (42%) 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 Iyo (33.7514°, 132.7014°, elevation 14 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.