Sai, Japan experiences average highs of 12°C (54°F) and lows of 10°C (50°F) throughout the year. Rainfall is frequent, averaging about 14 rainy days per month. Average highs have warmed by 1.9°C (3.4°F) across the available records.
Sai, Japan Weather & Climate 2026
Monthly climate averages for Sai, Japan. Based on 10-year ERA5 reanalysis data.
Climate Overview
Drier season: Mar–Oct 
Wetter season: Jan–Dec At-a-Glance Climate Summary
Live Weather & Air Quality
Key figures
Climate Score
4.2/10
Best: June, July, August, September
UV Index
4
Low
Temperature 12°C / 10°C
Feels Like 10°C / 5°C
Rainy Days 14
Rainfall 121 mm
Sunshine 8 h
Humidity 76%
Wind Speed 37 km/h
Dew Point 7°C
Snow Days 12 days
Frost Days 12 days
Hottest Month
24°C
August
Avg Low22°C
Rain13days
Coldest Month
-1°C
January
Avg High2°C
Rain22days
Driest Month
10days
May
Avg High14°C
Avg Low11°C
Windiest Month
46 km/h
December (Gusts 69)
Sea Temperature
7°C – 27°C
Warmest water: August (
27.4°C
)
Worst Time to Visit
Consider avoiding January, February, March, November due to very cold temperatures, heavy rainfall.
Sun Position
Sunrise 04:04
Daylight 15.2h
Sunset 19:13
Live conditions—
Sai on the map · live conditions
Sai, Japan
- Continent
- Asia
- Country
- Japan
- City
- Sai
- Population
- 1.9K
- Coordinates
- 41.43°, 140.86°
Seasonal Breakdown
Spring
Mar–May
Avg High 10°C
Avg Low 7°C
Rain 11 days/mo
Summer
Jun–Aug
Avg High 21°C
Avg Low 19°C
Rain 11 days/mo
3/3 best months
Autumn
Sep–Nov
Avg High 16°C
Avg Low 13°C
Rain 13 days/mo
1/3 best months
Winter
Dec–Feb
Avg High 3°C
Avg Low -1°C
Rain 22 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: 2°C / -1°C . Feb: 2°C / -1°C . Mar: 6°C / 3°C . Apr: 10°C / 7°C . May: 14°C / 11°C . Jun: 17°C / 15°C . Jul: 22°C / 20°C . Aug: 24°C / 22°C . Sep: 22°C / 20°C . Oct: 17°C / 14°C . Nov: 10°C / 6°C . Dec: 4°C / 1°C .
Monthly Rainfall
Rainfall
Bar chart showing monthly rainfall. Jan: 127 mm. Feb: 109 mm. Mar: 85 mm. Apr: 90 mm. May: 91 mm. Jun: 104 mm. Jul: 116 mm. Aug: 203 mm. Sep: 133 mm. Oct: 124 mm. Nov: 116 mm. Dec: 157 mm.
Monthly Humidity
Humidity
Line chart showing monthly humidity. Jan: 69%. Feb: 68%. Mar: 70%. Apr: 75%. May: 83%. Jun: 89%. Jul: 91%. Aug: 86%. Sep: 75%. Oct: 67%. Nov: 67%. Dec: 69%.
Monthly Wind Speed
Wind SpeedGusts
Bar chart showing monthly wind speed. Jan: 44 km/h . Feb: 44 km/h . Mar: 39 km/h . Apr: 37 km/h . May: 33 km/h . Jun: 29 km/h . Jul: 28 km/h . Aug: 33 km/h . Sep: 33 km/h . Oct: 37 km/h . Nov: 41 km/h . Dec: 46 km/h .
Sunshine
Sunshine
Sunshine: Jan: 7h. Feb: 8h. Mar: 9h. Apr: 10h. May: 10h. Jun: 10h. Jul: 9h. Aug: 9h. Sep: 9h. Oct: 8h. Nov: 7h. Dec: 6h.
Sea Temperature
Sea Temperatureswim
Line chart showing monthly sea temperature. Jan: 8°C . Feb: 7°C . Mar: 8°C . Apr: 11°C . May: 14°C . Jun: 19°C . Jul: 24°C . Aug: 27°C . Sep: 25°C . Oct: 20°C . Nov: 15°C . Dec: 10°C .
UV Index
UV Index
Bar chart showing monthly UV index. Jan: UV 2. Feb: UV 3. Mar: UV 4. Apr: UV 5. May: UV 6. Jun: UV 7. Jul: UV 7. Aug: UV 6. Sep: UV 5. Oct: UV 4. Nov: UV 3. Dec: UV 2.
Monthly Daylight Hours
Daylight12h reference
Monthly Dew Point & Comfort
Dew Point Dry Comfortable Humid Muggy Oppressive
Snow Days
Snow DaysSnowfall
Snow Days: Jan: 22 days. Feb: 20 days. Mar: 7 days. Apr: 1 days. May: 0 days. Jun: 0 days. Jul: 0 days. Aug: 0 days. Sep: 0 days. Oct: 0 days. Nov: 3 days. Dec: 19 days.
Climate Trends
Average highs have warmed by 1.9°C (3.4°F) across the available records. Average rainfall is trending wetter by about 20 mm.
2016 to 2025
Avg high Avg rainfall
Climate summary
| Last 12 months | All years | |
|---|---|---|
| Hottest month | Aug 2025 · 26°C | Aug · 24°C |
| Coldest month | Feb 2025 · 0°C | Jan · -1°C |
| Wettest month | Sep 2025 · 195 mm | Aug · 203 mm |
| Windiest month | Dec 2025 · 48 km/h | Dec · 46 km/h |
Month-by-Month Weather Table
January
Wet 
February
Wet March
Poor April
Poor May
Fair June best
Good July best
Excellent August best
Excellent September best
Excellent October
Fair November
Poor December
Wet | Month | Temp | Feels Like | Rain | Sun | Humidity | UV | Status | Details |
|---|---|---|---|---|---|---|---|---|
| January | 2°C / -1°C | -5°C / -9°C | 22days (127 mm) Wet | 6.7h Fair | 69% Muggy | 2.1 Moderate | Wet | View Details |
| February | 2°C / -1°C | -4°C / -9°C | 19days (109 mm) Wet | 7.7h Good | 68% Muggy | 3.1 Moderate | Wet | View Details |
| March | 6°C / 3°C | 1°C / -4°C | 13days (85 mm) Wet | 8.9h Good | 70% Muggy | 4.3 Moderate | Poor | View Details |
| April | 10°C / 7°C | 6°C / 1°C | 11days (90 mm) Wet | 9.5h Good | 75% Muggy | 5.4 High | Poor | View Details |
| May | 14°C / 11°C | 12°C / 7°C | 10days (91 mm) Wet | 10h Excellent | 83% Humid | 6.2 High | Fair | View Details |
| June best | 17°C / 15°C | 17°C / 13°C | 10days (104 mm) Wet | 9.7h Good | 89% Very Muggy | 6.5 High | Good | View Details |
| July best | 22°C / 20°C | 23°C / 20°C | 11days (116 mm) Wet | 9.1h Good | 91% Very Muggy | 6.6 High | Excellent | View Details |
| August best | 24°C / 22°C | 27°C / 22°C | 13days (203 mm) Wet | 8.5h Good | 86% Very Muggy | 6.1 High | Excellent | View Details |
| September best | 22°C / 20°C | 23°C / 18°C | 11days (133 mm) Wet | 8.5h Good | 75% Muggy | 5.3 High | Excellent | View Details |
| October | 17°C / 14°C | 14°C / 9°C | 13days (124 mm) Wet | 7.9h Good | 67% Muggy | 3.8 Moderate | Fair | View Details |
| November | 10°C / 6°C | 5°C / 0°C | 16days (116 mm) Wet | 6.7h Fair | 67% Muggy | 2.5 Moderate | Poor | View Details |
| December | 4°C / 1°C | -2°C / -8°C | 24days (157 mm) Wet | 6h Fair | 69% Muggy | 1.7 Low | Wet | View Details |
Compare Nearby City Climates
Frequently Asked Questions
The best months to visit Sai are June, July, August, September, when temperatures are comfortable and rainfall is at its lowest. This is based on 10-year climate averages for Sai, scoring temperature, rainfall, humidity, and sunshine hours.
The hottest month in Sai is August, with average daytime highs of 24°C (76°F). Plan outdoor activities for early morning or late afternoon if visiting during this period.
The coldest month in Sai is January, with average overnight lows of -1°C (30°F). Pack warm layers and expect shorter daylight hours during this period.
The wettest month in Sai is August, averaging 203mm of precipitation across 13 rainy days. An umbrella or waterproof jacket is essential.
The rainy season in Sai runs through December, January, February, November, with the heaviest rainfall in December. Based on 10-year averages for Sai.
Sai receives approximately 99 sunshine hours per year. The sunniest month is May with around 10 hours. Based on climate data for Sai.
The least favorable months to visit Sai are January, February, March, November, primarily due to very cold temperatures, heavy rainfall. For the best conditions, consider June, July, August, September instead.
The annual average UV index in Sai is 4, classified as moderate. Standard sun protection (sunscreen, hat) is recommended during prolonged outdoor exposure.
Average humidity in Sai is 76%, classified as humid. Humidity levels are generally comfortable and should not affect outdoor activities for most people.
Yes — sea temperatures in July, August, September average 26°C (79°F), which is warm and comfortable for swimming and water activities.
Yes, Sai receives snow. Months with snowfall average 12 snow days and 30 cm (12 in) of accumulation, with about 12 frost days during winter.
Average wind speeds in Sai are 37 km/h (23 mph). The windiest month is December with peak winds reaching 46 km/h (28 mph) (gusts up to 69 km/h / 43 mph).
Sai averages 2 clear-sky days per month with overall cloud cover around 65%. The clearest skies occur in May.
The annual average dew point in Sai is 7°C (45°F), which feels dry and comfortable. Outdoor activities are comfortable year-round from a humidity standpoint.
Sai 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 Sai ranges from 5°C (41°F) to 10°C (50°F) on average. Wind chill makes winters feel noticeably colder than the actual temperature — layered clothing is recommended.
Yes, June is a great time to visit Sai. It earns a climate score of 7.1/10 with Good.
For June in Sai, pack Layered clothing, Light jacket, Umbrella, Waterproof jacket, Comfortable walking shoes. With average highs of 17°C (63°F) and 10 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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