Isa, Japan experiences average highs of 21°C (70°F) and lows of 14°C (57°F) throughout the year. Rainfall is frequent, averaging about 13 rainy days per month. Average highs have stayed broadly stable across the available records.
Isa, Japan Weather & Climate 2026
Monthly climate averages for Isa, Japan. Based on 10-year ERA5 reanalysis data.
Climate Overview
Drier season: Jan–Dec 
Wetter season: Mar–Sep At-a-Glance Climate Summary
Live Weather & Air Quality
Key figures
Climate Score
5.6/10
Best: April, May, October
UV Index
5
Low
Temperature 21°C / 14°C
Feels Like 22°C / 14°C
Rainy Days 13
Rainfall 203 mm
Sunshine 8 h
Humidity 81%
Wind Speed 14 km/h
Dew Point 14°C
Snow Days 2 days
Frost Days 3 days
Hottest Month
31°C
August
Avg Low25°C
Rain17days
Coldest Month
3°C
January
Avg High10°C
Rain10days
Driest Month
8days
December
Avg High12°C
Avg Low5°C
Windiest Month
16 km/h
February (Gusts 42)
Sea Temperature
13°C – 30°C
Warmest water: August (
29.6°C
)
Worst Time to Visit
Consider avoiding January, February, July, August due to frequent rain.
Sun Position
Sunrise 05:12
Daylight 14.2h
Sunset 19:26
Live conditions—
Isa on the map · live conditions
Isa, Japan
- Continent
- Asia
- Country
- Japan
- City
- Isa
- Population
- 24.5K
- Coordinates
- 32.07°, 130.61°
Seasonal Breakdown
Spring
Mar–May
Avg High 20°C
Avg Low 12°C
Rain 13 days/mo
2/3 best months
Summer
Jun–Aug
Avg High 29°C
Avg Low 23°C
Rain 19 days/mo
Autumn
Sep–Nov
Avg High 23°C
Avg Low 16°C
Rain 12 days/mo
1/3 best months
Winter
Dec–Feb
Avg High 11°C
Avg Low 4°C
Rain 10 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: 10°C / 3°C . Feb: 11°C / 4°C . Mar: 16°C / 8°C . Apr: 20°C / 12°C . May: 24°C / 16°C . Jun: 26°C / 20°C . Jul: 30°C / 24°C . Aug: 31°C / 25°C . Sep: 28°C / 22°C . Oct: 24°C / 17°C . Nov: 18°C / 10°C . Dec: 12°C / 5°C .
Monthly Rainfall
Rainfall
Bar chart showing monthly rainfall. Jan: 77 mm. Feb: 117 mm. Mar: 172 mm. Apr: 188 mm. May: 274 mm. Jun: 475 mm. Jul: 368 mm. Aug: 229 mm. Sep: 220 mm. Oct: 137 mm. Nov: 109 mm. Dec: 74 mm.
Monthly Humidity
Humidity
Line chart showing monthly humidity. Jan: 77%. Feb: 77%. Mar: 78%. Apr: 79%. May: 81%. Jun: 87%. Jul: 88%. Aug: 85%. Sep: 85%. Oct: 81%. Nov: 80%. Dec: 78%.
Monthly Wind Speed
Wind SpeedGusts
Bar chart showing monthly wind speed. Jan: 15 km/h . Feb: 16 km/h . Mar: 15 km/h . Apr: 14 km/h . May: 13 km/h . Jun: 13 km/h . Jul: 13 km/h . Aug: 12 km/h . Sep: 12 km/h . Oct: 12 km/h . Nov: 13 km/h . Dec: 15 km/h .
Sunshine
Sunshine
Sunshine: Jan: 7h. Feb: 7h. Mar: 8h. Apr: 8h. May: 8h. Jun: 7h. Jul: 9h. Aug: 10h. Sep: 9h. Oct: 8h. Nov: 8h. Dec: 7h.
Sea Temperature
Sea Temperatureswim
Line chart showing monthly sea temperature. Jan: 14°C . Feb: 13°C . Mar: 14°C . Apr: 16°C . May: 19°C . Jun: 23°C . Jul: 28°C . Aug: 30°C . Sep: 29°C . Oct: 26°C . Nov: 22°C . Dec: 17°C .
UV Index
UV Index
Bar chart showing monthly UV index. Jan: UV 4. Feb: UV 4. Mar: UV 5. Apr: UV 6. May: UV 6. Jun: UV 6. Jul: UV 7. Aug: UV 7. Sep: UV 7. Oct: UV 5. Nov: UV 4. Dec: UV 3.
Monthly Daylight Hours
Daylight12h reference
Monthly Dew Point & Comfort
Dew Point Dry Comfortable Humid Muggy
Snow Days
Snow DaysSnowfall
Snow Days: Jan: 2 days. Feb: 2 days. Mar: 0 days. Apr: 0 days. May: 0 days. Jun: 0 days. Jul: 0 days. Aug: 0 days. Sep: 0 days. Oct: 0 days. Nov: 0 days. Dec: 1 days.
Climate Trends
Average highs have stayed broadly stable across the available records. Average rainfall is trending drier by about 105 mm.
2016 to 2025
Avg high Avg rainfall
Climate summary
| Last 12 months | All years | |
|---|---|---|
| Hottest month | Jul 2025 · 31°C | Aug · 31°C |
| Coldest month | Jan 2025 · 2°C | Jan · 3°C |
| Wettest month | Jun 2025 · 381 mm | Jun · 475 mm |
| Windiest month | Feb 2025 · 18 km/h | Feb · 16 km/h |
Month-by-Month Weather Table
January
Poor 
February
Poor March
Fair April best
Wet May best
Excellent June
Wet July
Wet August
Wet September
Wet October best
Excellent November
Good December
Fair | Month | Temp | Feels Like | Rain | Sun | Humidity | UV | Status | Details |
|---|---|---|---|---|---|---|---|---|
| January | 10°C / 3°C | 7°C / 0°C | 10days (77 mm) Wet | 6.8h Fair | 77% Humid | 3.9 Moderate | Poor | View Details |
| February | 11°C / 4°C | 9°C / 1°C | 11days (117 mm) Wet | 7.1h Good | 77% Humid | 4.3 Moderate | Poor | View Details |
| March | 16°C / 8°C | 15°C / 5°C | 13days (172 mm) Wet | 7.6h Good | 78% Humid | 5.2 High | Fair | View Details |
| April best | 20°C / 12°C | 20°C / 11°C | 12days (188 mm) Wet | 8h Good | 79% Humid | 5.9 High | Wet | View Details |
| May best | 24°C / 16°C | 25°C / 16°C | 13days (274 mm) Wet | 7.8h Good | 81% Humid | 6.3 High | Excellent | View Details |
| June | 26°C / 20°C | 30°C / 23°C | 19days (475 mm) Wet | 6.6h Fair | 87% Very Muggy | 5.9 High | Wet | View Details |
| July | 30°C / 24°C | 35°C / 29°C | 21days (368 mm) Wet | 8.5h Good | 88% Very Muggy | 7.4 Very High | Wet | View Details |
| August | 31°C / 25°C | 36°C / 29°C | 17days (229 mm) Wet | 9.6h Good | 85% Humid | 7.2 Very High | Wet | View Details |
| September | 28°C / 22°C | 33°C / 26°C | 17days (220 mm) Wet | 8.5h Good | 85% Humid | 6.6 High | Wet | View Details |
| October best | 24°C / 17°C | 25°C / 17°C | 11days (137 mm) Wet | 7.9h Good | 81% Humid | 5 Moderate | Excellent | View Details |
| November | 18°C / 10°C | 17°C / 9°C | 9days (109 mm) Wet | 7.5h Good | 80% Humid | 4.1 Moderate | Good | View Details |
| December | 12°C / 5°C | 9°C / 2°C | 8days (74 mm) Wet | 6.9h Fair | 78% Humid | 3.4 Moderate | Fair | View Details |
Compare Nearby City Climates
Frequently Asked Questions
The best months to visit Isa are April, May, October, when temperatures are comfortable and rainfall is at its lowest. This is based on 10-year climate averages for Isa, scoring temperature, rainfall, humidity, and sunshine hours.
The hottest month in Isa is August, with average daytime highs of 31°C (87°F). Plan outdoor activities for early morning or late afternoon if visiting during this period.
The coldest month in Isa is January, with average overnight lows of 3°C (38°F). Pack warm layers and expect shorter daylight hours during this period.
The wettest month in Isa is June, averaging 475mm of precipitation across 19 rainy days. An umbrella or waterproof jacket is essential.
The rainy season in Isa runs through July, June, August, September, with the heaviest rainfall in July. Based on 10-year averages for Isa.
Isa receives approximately 93 sunshine hours per year. The sunniest month is August with around 10 hours. Based on climate data for Isa.
The least favorable months to visit Isa are January, February, July, August, primarily due to frequent rain. For the best conditions, consider April, May, October instead.
The annual average UV index in Isa is 5, classified as moderate. Standard sun protection (sunscreen, hat) is recommended during prolonged outdoor exposure.
Average humidity in Isa is 81%, classified as humid. High humidity makes warm temperatures feel significantly hotter — lightweight, breathable clothing is recommended.
Yes — sea temperatures in June, July, August, September, October average 27°C (81°F), which is warm and comfortable for swimming and water activities.
Yes, Isa receives snow. Months with snowfall average 2 snow days and 1 cm (0 in) of accumulation, with about 3 frost days during winter.
Average wind speeds in Isa are 14 km/h (9 mph). The windiest month is February with peak winds reaching 16 km/h (10 mph) (gusts up to 42 km/h / 26 mph).
Isa averages 3 clear-sky days per month with overall cloud cover around 62%. The clearest skies occur in November.
The annual average dew point in Isa is 14°C (57°F), which feels pleasant with low humidity. Outdoor activities are comfortable year-round from a humidity standpoint.
Isa 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 Isa ranges from 14°C (57°F) to 22°C (72°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 Isa, with a climate score of 6.1/10. Consider visiting during April, May, October instead for better conditions.
For June in Isa, pack Umbrella, Waterproof jacket, Waterproof shoes, Breathable clothing, Sunscreen (SPF 30+). With average highs of 26°C (79°F) and 19 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.
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