Saikai in Summer
In summer (June, July and August), Saikai sees average daytime highs around 27°C and overnight lows near 24°C, with 860 mm of rain over about 46 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 23°C in early June to 28°C by late August. The sky is clear or mostly clear about 25% of the time across summer, and the air most often feels miserable.
Summer is Saikai's 2nd-best season to visit on our travel score. For the whole year in context, see Saikai's year-round climate.
- Avg daytime high
- 27°C
- warmest season of the year
- Avg overnight low
- 24°C
- Rainfall
- 860 mm
- 46 wet days
- Avg wind
- 13 km/h
- Travel score
- 5.4
- 2nd-best season
- Months
- Jun · Jul · Aug
Temperature in Saikai in Summer
Over the season highs climb from about 23°C in early June to 28°C by late August.
A typical summer day in Saikai reaches about 27°C and drops to 24°C overnight. The warmest of the three months is August, the coolest June.
How summer really feels in Saikai
Once humidity and wind are folded in, summer brings about 37 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.
Saikai 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 | 10° / 7° | 70 | 9.6 | 0.5 | 10.1 | 2.1 |
| Feb | 10° / 7° | 85 | 9 | 0.4 | 10.8 | 2.4 |
| Mar | 13° / 9° | 134 | 11.1 | 0 | 11.7 | 3.6 |
| Apr | 17° / 13° | 158 | 10.7 | 0 | 12.8 | 5.3 |
| May | 21° / 17° | 177 | 10.4 | 0 | 13.7 | 6.3 |
| Jun | 24° / 21° | 372 | 15.8 | 0 | 14.1 | 5.7 |
| Jul | 27° / 25° | 306 | 16.2 | 0 | 14 | 5.3 |
| Aug | 29° / 26° | 182 | 14.1 | 0 | 13.2 | 5.2 |
| Sep | 26° / 23° | 188 | 11.3 | 0 | 12.2 | 6.5 |
| Oct | 22° / 19° | 109 | 6.7 | 0 | 11.2 | 7.4 |
| Nov | 17° / 14° | 98 | 8 | 0 | 10.3 | 5.8 |
| Dec | 12° / 9° | 81 | 9.2 | 0 | 9.9 | 3.3 |
Cloud cover in Summer
The sky is clear or mostly clear about 25% of the time across summer.
Chance of precipitation in Summer
Saikai gets around 860 mm of rain over 46 wet days across summer. The line is the day-by-day chance of measurable precipitation.
Humidity in Summer
Most of summer feels miserable — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Summer
Winds average 13 km/h across summer.
Sunrise & sunset in Summer
Daylight runs from about 14 hours in early June to 12 h 42 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 4.9 kWh/m².
Hazard calendar for Saikai
In summer, Saikai overlaps its pacific typhoon and rainy season season. The full year is below, with each hazard's peak months called out.
Saikai sits in the Pacific typhoon belt; the season peaks July–October.
Saikai's rainy season runs May–September, when most of the year's rain falls.
Is summer a good time to visit Saikai?
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 Saikai for sightseeing.
What to pack for Saikai in Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, Saikai sees daytime highs around 27°C and nights near 24°C. Pack light clothes and rain gear. Worth having: sun protection. About 46 days see rain.
Sea temperature near Saikai in Summer
The nearest coast averages about 25°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 13 km away) is warmest in August at about 27°C and coldest in February near 15°C.
It's comfortable for a long swim from May 27 to Nov 29 — about 6.1 months when the water holds above 20°C.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 16 | 15 | 16 | 17 | 19 | 22 | 25 | 27 | 26 | 24 | 21 | 19 |
| Comfort | Cool | Cool | Cool | Cool | Cool | Refreshing | Warm | Warm | Warm | Refreshing | Refreshing | Cool |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 16 | Cool |
| Feb | 15 | Cool |
| Mar | 16 | Cool |
| Apr | 17 | Cool |
| May | 19 | Cool |
| Jun | 22 | Refreshing |
| Jul | 25 | Warm |
| Aug | 27 | Warm |
| Sep | 26 | Warm |
| Oct | 24 | Refreshing |
| Nov | 21 | Refreshing |
| Dec | 19 | Cool |
UV index in Saikai 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 Saikai peaks around July 15 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 | 4 | 6 | 7 | 8 | 9 | 10 | 8 | 9 | 7 | 4 | 3 |
| Level | Moderate | Moderate | High | Very high | Very high | Very high | Extreme | Very high | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 3 | Moderate |
| Feb | 4 | Moderate |
| Mar | 6 | High |
| Apr | 7 | Very high |
| May | 8 | Very high |
| Jun | 9 | Very high |
| Jul | 10 | Extreme |
| Aug | 8 | Very high |
| Sep | 9 | Very high |
| Oct | 7 | High |
| Nov | 4 | Moderate |
| Dec | 3 | Moderate |
Air quality in Saikai 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 Saikai is worst in April — around 24 µg/m³ PM2.5 (moderate), about 2.1× 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) | 16 | 19 | 23 | 24 | 21 | 17 | 12 | 12 | 12 | 11 | 14 | 13 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Moderate | Good | Good | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 16 | Moderate |
| Feb | 19 | Moderate |
| Mar | 23 | Moderate |
| Apr | 24 | Moderate |
| May | 21 | Moderate |
| Jun | 17 | Moderate |
| Jul | 12 | Good |
| Aug | 12 | Moderate |
| Sep | 12 | Good |
| Oct | 11 | Good |
| Nov | 14 | Moderate |
| Dec | 13 | Moderate |
Where is Saikai?
Saikai sits at 33.0°N, 129.7°E, 184 m above sea level, in Japan. The nearest listed city is Sasebo, 21 km away.
Topography around Saikai
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Saikai.
Within 3 km, the terrain around Saikai has significant variations in elevation — a maximum elevation change of 353 m around an average of 182 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 564 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,455 m.
The land around Saikai is covered by trees (96%) within 3 km, water (55%) and trees (42%) within 16 km, and water (68%) and trees (24%) 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 Saikai (32.9839°, 129.6809°, elevation 184 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.