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December Weather in Joetsu, Japan

Last updated: August 23, 2025

In December, the average temperature in Joetsu, Japan hovers around 6°C (43°F). Expect some chilly spells with minimums dipping to -2°C (29°F), while the maximum can reach a pleasant 20°C (69°F). Be prepared for frequent rain, as precipitation averages 273 mm (10.7 in) over 24 days. With an average humidity of 86%, it's a month where that cozy sweater will become your best friend!

December Temperature in Joetsu

In December in Joetsu, the average temperature is 6°C (43°F). Maximum temperatures can reach 20°C (69°F), while minimums can drop as low as -2°C (29°F). This variation in temperature means travelers should be prepared for both mild days and chilly nights.

December Weather in Joetsu: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Joetsu, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Joetsu, December typically has an average temperature of 6°C (43°F), with highs reaching up to 20°C (69°F) and lows dropping to around -2°C (29°F).
JanFebMarAprMayJunJulAugSepOctNovDec383946536370788173645343
Data source: Temperature data for Joetsu generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Joetsu

In Joetsu in December, the precipitation amount is 273 mm (10.7 in) over the course of 24 days.

December Precipitation Trends in Joetsu

The chart displays monthly precipitation patterns in Joetsu, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In Joetsu, December typically receives around 273 mm (10.7 inches) of precipitation spread over approximately 24 days.
JanFebMarAprMayJunJulAugSepOctNovDec233181128121105105290157171190170273
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Joetsu

In Joetsu in December humidity is 86%. With an average temperature of 6°C (43°F), this humidity feels like a chilling blanket enveloping you, making outdoor exploration feel damp and uncomfortable.

December Average Humidity in Joetsu

This chart illustrates the average monthly humidity levels in Joetsu, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in Joetsu is approximately 86%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%87%81%79%81%88%92%92%89%87%85%86%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Joetsu

In Joetsu in December, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Joetsu, you can check the information here.

Maximum UV Index Levels in Joetsu for December

The chart shows the monthly maximum UV Index (UVI) for Joetsu in December, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In December, the maximum UV index in Joetsu typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3589101111119653
Data source: Joetsu December UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How December Weather in Joetsu Compares to Other Months

Weather in Joetsu varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Joetsu, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Joetsu, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather3°C (38°F)233 mm (9.2 inches)88%moderate
February Weather4°C (39°F)181 mm (7.1 inches)86%moderate
March Weather8°C (46°F)128 mm (5.0 inches)81%very high
April Weather12°C (53°F)121 mm (4.7 inches)78%very high
May Weather17°C (64°F)105 mm (4.1 inches)81%very high
June Weather21°C (70°F)105 mm (4.1 inches)88%extreme
July Weather26°C (79°F)290 mm (11.4 inches)92%extreme
August Weather27°C (82°F)157 mm (6.2 inches)92%extreme
September Weather23°C (74°F)171 mm (6.7 inches)89%very high
October Weather18°C (64°F)190 mm (7.5 inches)87%high
November Weather12°C (53°F)170 mm (6.7 inches)85%moderate
December Weather6°C (43°F)273 mm (10.7 inches)86%moderate

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