Kasugayama CastleReport this photo · linked, not stored
Jōetsu climate by month
What the weather is like
Jōetsu has a humid subtropical climate (Köppen Cfa): rain spread through the year and no real dry season.
The warmest month is August, when afternoons average 30° and nights 23°. January is the coolest month, with highs of 5° and lows of 0°. The difference between the warmest and the coolest month is about 24°, a large swing typical of continental interiors.
About 2,498 mm of precipitation falls in an average year. December is the wettest month (354 mm, 26 wet days) and April the driest (94 mm, 13 wet days). Cloud cover ranges from 38% in August to 54% in June.
The sea reaches about 27° in August. Sea temperatures lag the air by a month or two, so late summer is usually warmer for swimming than early summer.
Compared with Tokyo, the capital, Jōetsu is 0.2° warmer on a August afternoon and receives more precipitation over the year.
Year in figures
- Hottest afternoons
- 30° · August
- Coldest nights
- 0° · January
- Wettest month
- December
- Driest month
- April
- Clearest skies
- August · 38% cloud
- Warmest sea
- 27° · August
- Longest day
- 14 h 42 min
- Shortest day
- 9 h 38 min
Twelve months at a glance
Temperature and precipitation
Daily high/low range bars, monthly precipitation columns, sea temperature lineTemperature curve
Average high, low and seaDaylight
Hours between sunrise and sunset on the 15th of each monthClimate normals month by month
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Average high | 5° | 5° | 9° | 15° | 21° | 24° | 28° | 30° | 25° | 20° | 14° | 8° |
| Average low | 0° | 0° | 2° | 7° | 12° | 17° | 21° | 23° | 19° | 13° | 7° | 2° |
| Precipitation | 365 mm | 229 mm | 176 mm | 94 mm | 98 mm | 146 mm | 203 mm | 146 mm | 192 mm | 195 mm | 300 mm | 354 mm |
| Wet days (≥1 mm) | 25 | 18.5 | 14.2 | 12.7 | 13.7 | 14 | 19.7 | 20 | 19.7 | 16.7 | 18.2 | 25.5 |
| Cloud cover | 50% | 49% | 47% | 42% | 47% | 54% | 50% | 38% | 47% | 42% | 42% | 45% |
| Sea temperature | 13° | 11° | 10° | 11° | 15° | 20° | 23° | 27° | 25° | 22° | 19° | 15° |
| Daylight | 9h 53 | 10h 49 | 11h 54 | 13h 07 | 14h 08 | 14h 42 | 14h 29 | 13h 37 | 12h 28 | 11h 18 | 10h 13 | 9h 38 |
| Month score | 17 | 17 | 18 | 51 | 61 | 57 | 48 | 44 | 59 | 62 | 39 | 19 |