Winter Weather in Koshima Japan

Daily high temperatures decrease by 4°F, from 64°F to 61°F, rarely falling below 49°F or exceeding 71°F. The lowest daily average high temperature is 57°F on January 26.

Daily low temperatures decrease by 5°F, from 56°F to 52°F, rarely falling below 42°F or exceeding 63°F. The lowest daily average low temperature is 49°F on January 26.

For reference, on August 1, the hottest day of the year, temperatures in Koshima typically range from 77°F to 86°F, while on January 26, the coldest day of the year, they range from 49°F to 57°F.

The figure below shows you a compact characterization of the hourly average winter temperatures. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Salakta, Tunisia (6,444 miles away); Ródos, Greece (5,625 miles); and Rizokárpaso, Cyprus (5,355 miles) are the far-away foreign places with temperatures most similar to Koshima (view comparison).

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The winter in Koshima experiences increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 27% to 37%. The lowest chance of overcast or mostly cloudy conditions is 23% on December 14.

The clearest day of the winter is December 14, with clear, mostly clear, or partly cloudy conditions 77% of the time.

For reference, on June 22, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 81%, while on December 14, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 77%.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Koshima, the chance of a wet day over the course of the winter is rapidly increasing, starting the season at 37% and ending it at 44%.

For reference, the year's highest daily chance of a wet day is 68% on June 22, and its lowest chance is 33% on December 14.

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the winter in Koshima is rapidly increasing, starting the season at 4.8 inches, when it rarely exceeds 8.2 inches or falls below 2.1 inches, and ending the season at 6.7 inches, when it rarely exceeds 10.3 inches or falls below 3.7 inches.

The lowest average 31-day accumulation is 4.0 inches on December 27.

Over the course of the winter in Koshima, the length of the day is rapidly increasing. From the start to the end of the season, the length of the day increases by 1 hour, 10 minutes, implying an average daily increase of 47 seconds, and weekly increase of 5 minutes, 31 seconds.

The shortest day of the winter is December 21, with 10 hours, 12 minutes of daylight and the longest day is February 28, with 11 hours, 31 minutes of daylight.

The latest sunrise of the winter in Koshima is 7:15 AM on January 10 and the earliest sunrise is 30 minutes earlier at 6:45 AM on February 28.

The earliest sunset is 5:17 PM on December 2 and the latest sunset is 59 minutes later at 6:15 PM on February 28.

Daylight saving time is not observed in Koshima during 2024.

For reference, on June 20, the longest day of the year, the Sun rises at 5:16 AM and sets 14 hours, 6 minutes later, at 7:22 PM, while on December 21, the shortest day of the year, it rises at 7:10 AM and sets 10 hours, 12 minutes later, at 5:21 PM.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

The figure below presents a compact representation of key lunar data for the winter of 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Koshima is essentially constant during the winter, remaining within 2% of 2% throughout.

The lowest chance of a muggy day during the winter is 0% on January 25.

For reference, on August 4, the muggiest day of the year, there are muggy conditions 100% of the time, while on January 25, the least muggy day of the year, there are muggy conditions 0% of the time.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Koshima is gradually increasing during the winter, increasing from 15.8 miles per hour to 16.7 miles per hour over the course of the season.

For reference, on January 18, the windiest day of the year, the daily average wind speed is 17.4 miles per hour, while on July 11, the calmest day of the year, the daily average wind speed is 11.7 miles per hour.

The highest daily average wind speed during the winter is 17.4 miles per hour on January 18.

The hourly average wind direction in Koshima throughout the winter is predominantly from the north, with a peak proportion of 62% on January 22.

Koshima is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature in Koshima is decreasing during the winter, falling by 6°F, from 74°F to 68°F, over the course of the season.

The lowest average surface water temperature during the winter is 68°F on February 16.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in Koshima are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Koshima are very rapidly decreasing during the winter, decreasing by 5,918°F, from 6,188°F to 270°F, over the course of the season.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Koshima is increasing during the winter, rising by 1.2 kWh, from 3.0 kWh to 4.2 kWh, over the course of the season.

The lowest average daily incident shortwave solar energy during the winter is 2.9 kWh on December 24.

For the purposes of this report, the geographical coordinates of Koshima are 30.235 deg latitude, 130.535 deg longitude, and 161 ft elevation.

The topography within 2 miles of Koshima contains extreme variations in elevation, with a maximum elevation change of 3,389 feet and an average elevation above sea level of 520 feet. Within 10 miles also contains extreme variations in elevation (6,296 feet). Within 50 miles also contains extreme variations in elevation (6,316 feet).

The area within 2 miles of Koshima is covered by water (55%) and trees (39%), within 10 miles by water (69%) and trees (30%), and within 50 miles by water (96%).