Onna, Japan experiences average highs of 24°C (75°F) and lows of 22°C (72°F) throughout the year. Rainfall is frequent, averaging about 13 rainy days per month. Average highs have stayed broadly stable across the available records.
Onna, Japan Weather & Climate 2026
Monthly climate averages for Onna, Japan. Based on 10-year ERA5 reanalysis data.
Climate Overview
Drier season: Jan–Nov 
Wetter season: Mar–Dec At-a-Glance Climate Summary
Live Weather & Air Quality
Key figures
Climate Score
6.1/10
Best: March, April, May, October, November
UV Index
6
High
Temperature 24°C / 22°C
Feels Like 26°C / 22°C
Rainy Days 13
Rainfall 162 mm
Sunshine 8 h
Humidity 76%
Wind Speed 32 km/h
Dew Point 19°C
Hottest Month
30°C
August
Avg Low28°C
Rain14days
Coldest Month
17°C
January
Avg High19°C
Rain12days
Driest Month
11days
November
Avg High24°C
Avg Low22°C
Windiest Month
37 km/h
December (Gusts 52)
Sea Temperature
21°C – 30°C
Warmest water: August (
29.7°C
)
Worst Time to Visit
Consider avoiding July, August due to frequent rain, oppressive humidity.
Sun Position
Sunrise 05:37
Daylight 13.8h
Sunset 19:24
Live conditions—
Onna on the map · live conditions
Onna, Japan
- Continent
- Asia
- Country
- Japan
- City
- Onna
- Population
- 10.9K
- Coordinates
- 26.50°, 127.85°
Seasonal Breakdown
Spring
Mar–May
Avg High 23°C
Avg Low 21°C
Rain 13 days/mo
3/3 best months
Summer
Jun–Aug
Avg High 29°C
Avg Low 27°C
Rain 14 days/mo
Autumn
Sep–Nov
Avg High 27°C
Avg Low 25°C
Rain 13 days/mo
2/3 best months
Winter
Dec–Feb
Avg High 20°C
Avg Low 17°C
Rain 12 days/mo
Climate Charts
Based on historical averages (2016–2025)
Monthly Temperatures
HighLowShaded bands show the typical range across the available yearly records.
Line chart showing monthly temperatures. Jan: 19°C / 17°C . Feb: 19°C / 17°C . Mar: 21°C / 18°C . Apr: 23°C / 21°C . May: 25°C / 23°C . Jun: 28°C / 26°C . Jul: 29°C / 28°C . Aug: 30°C / 28°C . Sep: 29°C / 27°C . Oct: 27°C / 25°C . Nov: 24°C / 22°C . Dec: 21°C / 19°C .
Monthly Rainfall
Rainfall
Bar chart showing monthly rainfall. Jan: 117 mm. Feb: 96 mm. Mar: 124 mm. Apr: 155 mm. May: 246 mm. Jun: 270 mm. Jul: 153 mm. Aug: 195 mm. Sep: 180 mm. Oct: 138 mm. Nov: 126 mm. Dec: 145 mm.
Monthly Humidity
Humidity
Line chart showing monthly humidity. Jan: 65%. Feb: 68%. Mar: 71%. Apr: 77%. May: 83%. Jun: 87%. Jul: 84%. Aug: 82%. Sep: 81%. Oct: 74%. Nov: 70%. Dec: 67%.
Monthly Wind Speed
Wind SpeedGusts
Bar chart showing monthly wind speed. Jan: 35 km/h . Feb: 35 km/h . Mar: 32 km/h . Apr: 30 km/h . May: 29 km/h . Jun: 30 km/h . Jul: 29 km/h . Aug: 28 km/h . Sep: 29 km/h . Oct: 32 km/h . Nov: 34 km/h . Dec: 37 km/h .
Sunshine
Sunshine
Sunshine: Jan: 5h. Feb: 6h. Mar: 8h. Apr: 9h. May: 9h. Jun: 9h. Jul: 11h. Aug: 11h. Sep: 10h. Oct: 9h. Nov: 7h. Dec: 5h.
Sea Temperature
Sea Temperatureswim
Line chart showing monthly sea temperature. Jan: 22°C . Feb: 21°C . Mar: 21°C . Apr: 23°C . May: 24°C . Jun: 27°C . Jul: 30°C . Aug: 30°C . Sep: 30°C . Oct: 29°C . Nov: 26°C . Dec: 24°C .
UV Index
UV Index
Bar chart showing monthly UV index. Jan: UV 4. Feb: UV 5. Mar: UV 6. Apr: UV 7. May: UV 7. Jun: UV 7. Jul: UV 8. Aug: UV 8. Sep: UV 7. Oct: UV 6. Nov: UV 5. Dec: UV 4.
Monthly Daylight Hours
Daylight12h reference
Monthly Dew Point & Comfort
Dew Point Dry Comfortable Humid Muggy
Climate Trends
Average highs have stayed broadly stable across the available records. Average rainfall is trending drier by about 40 mm.
2016 to 2025
Avg high Avg rainfall
Climate summary
| Last 12 months | All years | |
|---|---|---|
| Hottest month | Sep 2025 · 30°C | Aug · 30°C |
| Coldest month | Feb 2025 · 15°C | Jan · 17°C |
| Wettest month | Jul 2025 · 244 mm | Jun · 270 mm |
| Windiest month | Nov 2025 · 36 km/h | Dec · 37 km/h |
Month-by-Month Weather Table
January
Fair 
February
Good March best
Good April best
Excellent May best
Excellent June
Wet July
Poor August
Wet September
Wet October best
Excellent November best
Excellent December
Fair | Month | Temp | Feels Like | Rain | Sun | Humidity | UV | Status | Details |
|---|---|---|---|---|---|---|---|---|
| January | 19°C / 17°C | 17°C / 13°C | 12days (117 mm) Wet | 5.4h Fair | 65% Muggy | 4.3 Moderate | Fair | View Details |
| February | 19°C / 17°C | 17°C / 13°C | 12days (96 mm) Wet | 6.3h Fair | 68% Muggy | 4.8 Moderate | Good | View Details |
| March best | 21°C / 18°C | 20°C / 16°C | 13days (124 mm) Wet | 7.8h Good | 71% Muggy | 6.3 High | Good | View Details |
| April best | 23°C / 21°C | 23°C / 19°C | 12days (155 mm) Wet | 8.8h Good | 77% Humid | 7.1 Very High | Excellent | View Details |
| May best | 25°C / 23°C | 28°C / 24°C | 15days (246 mm) Wet | 9h Good | 83% Humid | 6.8 High | Excellent | View Details |
| June | 28°C / 26°C | 32°C / 28°C | 17days (270 mm) Wet | 9.2h Good | 87% Very Muggy | 7.1 Very High | Wet | View Details |
| July | 29°C / 28°C | 35°C / 31°C | 12days (153 mm) Wet | 11.1h Excellent | 84% Humid | 8 Very High | Poor | View Details |
| August | 30°C / 28°C | 35°C / 31°C | 14days (195 mm) Wet | 10.8h Excellent | 82% Humid | 7.9 Very High | Wet | View Details |
| September | 29°C / 27°C | 33°C / 29°C | 16days (180 mm) Wet | 9.8h Good | 81% Humid | 7.4 Very High | Wet | View Details |
| October best | 27°C / 25°C | 29°C / 25°C | 12days (138 mm) Wet | 9h Good | 74% Muggy | 6.1 High | Excellent | View Details |
| November best | 24°C / 22°C | 24°C / 20°C | 11days (126 mm) Wet | 7.2h Good | 70% Muggy | 4.7 Moderate | Excellent | View Details |
| December | 21°C / 19°C | 19°C / 15°C | 13days (145 mm) Wet | 5.2h Fair | 67% Muggy | 3.7 Moderate | Fair | View Details |
Compare Nearby City Climates
Frequently Asked Questions
The best months to visit Onna are March, April, May, October, November, when temperatures are comfortable and rainfall is at its lowest. This is based on 10-year climate averages for Onna, scoring temperature, rainfall, humidity, and sunshine hours.
The hottest month in Onna is August, with average daytime highs of 30°C (85°F). Plan outdoor activities for early morning or late afternoon if visiting during this period.
The coldest month in Onna is January, with average overnight lows of 17°C (62°F). Pack warm layers and expect shorter daylight hours during this period.
The wettest month in Onna is June, averaging 270mm of precipitation across 17 rainy days. An umbrella or waterproof jacket is essential.
The rainy season in Onna runs through June, September, May, August, with the heaviest rainfall in June. Based on 10-year averages for Onna.
Onna receives approximately 100 sunshine hours per year. The sunniest month is July with around 11 hours. Based on climate data for Onna.
The least favorable months to visit Onna are July, August, primarily due to frequent rain, oppressive humidity. For the best conditions, consider March, April, May, October, November instead.
The annual average UV index in Onna is 6, classified as high. Standard sun protection (sunscreen, hat) is recommended during prolonged outdoor exposure.
Average humidity in Onna is 76%, classified as humid. Humidity levels are generally comfortable and should not affect outdoor activities for most people.
Yes — sea temperatures in January, April, May, June, July, August, September, October, November, December average 26°C (79°F), which is warm and comfortable for swimming and water activities.
Average wind speeds in Onna are 32 km/h (20 mph). The windiest month is December with peak winds reaching 37 km/h (23 mph) (gusts up to 52 km/h / 32 mph).
Onna averages 3 clear-sky days per month with overall cloud cover around 64%. The clearest skies occur in August.
The annual average dew point in Onna is 19°C (66°F), which feels noticeably humid. Summer months may feel slightly sticky, but conditions remain manageable for most people.
Onna has a Humid Subtropical climate, classified as Cfa under the Köppen system. Temperate climates have mild winters and warm summers, with rainfall spread across the year and four distinct seasons.
The 'feels like' temperature in Onna ranges from 22°C (72°F) to 26°C (79°F) on average. The 'feels like' temperature closely matches the actual temperature throughout most of the year.
June is not the best time to visit Onna, with a climate score of 5.2/10. Consider visiting during March, April, May, October, November instead for better conditions.
For June in Onna, pack Umbrella, Waterproof jacket, Waterproof shoes, Breathable clothing, Sunscreen (SPF 30+). With average highs of 28°C (82°F) and 17 rainy days, these essentials will keep you comfortable.
Data Source
Climate data derived from ERA5 reanalysis (ECMWF), averaged over 2016–2025. Sea surface temperature from marine reanalysis data. Climate scores and seasonal estimates are computed by WorldStats.
Last updated: