Iwai in Spring
In spring (March, April and May), Iwai sees average daytime highs around 16°C and overnight lows near 7°C, with 452 mm of precipitation over about 45 wet days across the season. It is the 3rd-warmest season and the 3rd-wettest season.
Over the season highs climb from about 9°C in early March to 22°C by late May. The sky is clear or mostly clear about 25% of the time across spring, and the air most often feels dry.
Spring is Iwai's 3rd-best season to visit on our travel score. For the whole year in context, see Iwai's year-round climate.
- Avg daytime high
- 16°C
- 3rd-warmest season
- Avg overnight low
- 7°C
- Precipitation
- 452 mm
- 45 wet days
- Avg wind
- 7 km/h
- Travel score
- 4.2
- 3rd-best season
- Months
- Mar · Apr · May
Temperature in Iwai in Spring
Over the season highs climb from about 9°C in early March to 22°C by late May.
A typical spring day in Iwai reaches about 16°C and drops to 7°C overnight. The warmest of the three months is May, the coolest March.
How spring really feels in Iwai
Once humidity and wind are folded in, spring brings about 0 days that feel above 32°C and 18 that feel at or below 0°C.
The story in spring is cold — wind chill drags the overnight "feels like" below the raw low.
Iwai weather by month
How the three spring months (March, April and May) 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 | 9.9 | 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 Spring
The sky is clear or mostly clear about 25% of the time across spring.
Chance of precipitation in Spring
Iwai gets around 452 mm of rain and snow over 45 wet days across spring. The line is the day-by-day chance of measurable precipitation.
Humidity in Spring
Most of spring feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Spring
Winds average 7 km/h across spring.
Sunrise & sunset in Spring
Daylight runs from about 11 h 12 min in early March to 14 h 12 min by late May. The lit band spans sunrise to sunset each day.
Solar energy in Spring
Average shortwave solar energy reaching the ground each day across spring, about 4.7 kWh/m².
Hazard calendar for Iwai
In spring, Iwai overlaps its pacific typhoon season. The full year is below, with each hazard's peak months called out.
Iwai sits in the Pacific typhoon belt; the season peaks July–October.
Is spring a good time to visit Iwai?
Our two travel scores rate spring for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
spring is a reasonable time to visit Iwai for sightseeing.
What to pack for Iwai in Spring
From spring's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In spring, Iwai sees daytime highs around 16°C and nights near 7°C. Pack a warm layer and rain gear. Worth having: sun protection. About 45 days see rain.
Sea temperature near Iwai in Spring
The nearest coast averages about 15°C across spring — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 60 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 Iwai in Spring
Clear-sky midday UV across spring 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 Iwai peaks around July 16 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 | 5 | 7 | 9 | 9 | 10 | 9 | 9 | 6 | 4 | 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 | 5 | Moderate |
| Apr | 7 | High |
| May | 9 | Very high |
| Jun | 9 | Very high |
| Jul | 10 | Very high |
| Aug | 9 | Very high |
| Sep | 9 | Very high |
| Oct | 6 | High |
| Nov | 4 | Moderate |
| Dec | 2 | Moderate |
Air quality in Iwai in Spring
Average fine-particle pollution (PM2.5) through the year — so you can see where spring falls, not just the annual average.
Air quality in Iwai 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 Iwai?
Iwai sits at 35.8°N, 139.2°E, 321 m above sea level, in Japan. The nearest listed city is Akiruno, 2.0 km away.
Topography around Iwai
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Iwai.
Within 3 km, the terrain around Iwai has significant variations in elevation — a maximum elevation change of 387 m around an average of 279 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,339 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,737 m.
The land around Iwai is covered by trees (82%) within 3 km, trees (73%) and artificial surfaces (22%) within 16 km, and trees (48%) and artificial surfaces (27%) 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 Iwai (35.75°, 139.2333°, elevation 321 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.