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Climate and Average Weather Year Round in Koshima Japan

In Koshima, the summers are warm, oppressive, windy, and mostly cloudy; the winters are cold, extremely windy, and mostly clear; and it is wet year round. Over the course of the year, the temperature typically varies from 49°F to 86°F and is rarely below 42°F or above 89°F.

Based on the tourism score, the best time of year to visit Koshima for warm-weather activities is from late September to early November.

Climate in Koshima

coolcomfortablewarmhotwarmcomfortablecoolJanFebMarAprMayJunJulAugSepOctNovDecNowNow77%77%19%19%clearovercastprecipitation: 18.0 inprecipitation: 18.0 in4.0 in4.0 inmuggy: 100%muggy: 100%0%0%drydrytourism score: 7.3tourism score: 7.32.32.3
Koshima weather by month. Click on each chart for more information.

Average Temperature in Koshima

The hot season lasts for 3.2 months, from June 19 to September 27, with an average daily high temperature above 80°F. The hottest day of the year is August 2, with an average high of 86°F and low of 77°F.

The cool season lasts for 3.1 months, from December 9 to March 13, with an average daily high temperature below 63°F. The coldest day of the year is January 26, with an average low of 49°F and high of 57°F.

Average High and Low Temperature in Koshima

Average High and Low Temperature in KoshimahotcoolcoolJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F10°F10°F20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°F100°F100°FJan 2657°FJan 2657°FAug 286°FAug 286°F49°F49°F77°F77°FJun 1980°FJun 1980°FSep 2780°FSep 2780°FDec 963°FDec 963°FMar 1363°FMar 1363°F72°F72°F72°F72°F55°F55°F53°F53°FNowNow
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

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

Average Hourly Temperature in Koshima

Average Hourly Temperature in KoshimaJanFebMarAprMayJunJulAugSepOctNovDec12 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMNowNowcoldcoldcoolcoolcomfortablecomfortablewarmhotcoldcold
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

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).

Compare Koshima to another city:

Clouds

In Koshima, the average percentage of the sky covered by clouds experiences extreme seasonal variation over the course of the year.

The clearer part of the year in Koshima begins around September 9 and lasts for 6.6 months, ending around March 28. On December 15, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 77% of the time, and overcast or mostly cloudy 23% of the time.

The cloudier part of the year begins around March 28 and lasts for 5.4 months, ending around September 9. On June 23, the cloudiest day of the year, the sky is overcast or mostly cloudy 81% of the time, and clear, mostly clear, or partly cloudy 19% of the time.

Cloud Cover Categories in Koshima

Cloud Cover Categories in KoshimaclearerclearercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Dec 1577%Dec 1577%Jun 2319%Jun 2319%Sep 948%Sep 948%Mar 2848%Mar 2848%NowNowclearmostly clearovercastpartly cloudy
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Koshima varies significantly throughout the year.

The wetter season lasts 3.6 months, from March 22 to July 10, with a greater than 51% chance of a given day being a wet day. The chance of a wet day peaks at 68% on June 23.

The drier season lasts 8.4 months, from July 10 to March 22. The smallest chance of a wet day is 33% on December 15.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 68% on June 23.

Daily Chance of Precipitation in Koshima

Daily Chance of Precipitation in KoshimawetdrydryJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Jun 2368%Jun 2368%Dec 1533%Dec 1533%Mar 2251%Mar 2251%Jul 1051%Jul 1051%NowNowrain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Koshima experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in Koshima. The most rain falls during the 31 days centered around June 17, with an average total accumulation of 18.0 inches.

The least rain falls around December 28, with an average total accumulation of 4.0 inches.

Average Monthly Rainfall in Koshima

Average Monthly Rainfall in KoshimaJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in5 in5 in10 in10 in15 in15 in20 in20 in25 in25 in30 in30 inJun 1718.0 inJun 1718.0 inDec 284.0 inDec 284.0 inSep 188.9 inSep 188.9 inNowNow
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

The length of the day in Koshima varies significantly over the course of the year. In 2021, the shortest day is December 22, with 10 hours, 12 minutes of daylight; the longest day is June 21, with 14 hours, 6 minutes of daylight.

Hours of Daylight and Twilight in Koshima

Hours of Daylight and Twilight in KoshimaJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 7 minMar 2012 hr, 7 minMar 2014 hr, 6 minJun 2114 hr, 6 minJun 2112 hr, 9 minSep 2312 hr, 9 minSep 2310 hr, 12 minDec 2210 hr, 12 minDec 22nightnightdayNowNow
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 5:15 AM on June 11, and the latest sunrise is 2 hours, 0 minutes later at 7:15 AM on January 10. The earliest sunset is at 5:17 PM on December 2, and the latest sunset is 2 hours, 7 minutes later at 7:23 PM on July 1.

Daylight saving time (DST) is not observed in Koshima during 2021.

Sunrise & Sunset with Twilight in Koshima

Sunrise & Sunset with Twilight in KoshimaJanFebMarAprMayJunJulAugSepOctNovDec2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 115:15 AMJun 115:15 AM7:23 PMJul 17:23 PMJul 1Dec 25:17 PMDec 25:17 PM7:15 AMJan 107:15 AMJan 10daynightnightSolarMidnightSolarMidnightSolarNoonSunriseSunsetNowNow
The solar day over the course of the year 2021. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Moon

The figure below presents a compact representation of key lunar data for 2021. 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.

Moon Rise, Set & Phases in Koshima

The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.

Humidity

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.

Koshima experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 5.6 months, from May 9 to October 28, during which time the comfort level is muggy, oppressive, or miserable at least 25% of the time. The muggiest day of the year is August 6, with muggy conditions 100% of the time.

The least muggy day of the year is January 25, when muggy conditions are essentially unheard of.

Humidity Comfort Levels in Koshima

Humidity Comfort Levels in KoshimamuggyJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Jan 250%Jan 250%100%Aug 6100%Aug 6May 925%May 925%Oct 2825%Oct 2825%NowNowmiserablemiserableoppressiveoppressivedrydrymuggymuggyhumidhumid
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

Wind

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 experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 5.0 months, from November 14 to April 14, with average wind speeds of more than 14.6 miles per hour. The windiest day of the year is January 18, with an average hourly wind speed of 17.4 miles per hour.

The calmer time of year lasts for 7.0 months, from April 14 to November 14. The calmest day of the year is July 12, with an average hourly wind speed of 11.7 miles per hour.

Average Wind Speed in Koshima

Average Wind Speed in KoshimawindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph0 mph5 mph5 mph10 mph10 mph15 mph15 mph20 mph20 mph25 mph25 mphJan 1817.4 mphJan 1817.4 mphJul 1211.7 mphJul 1211.7 mphNov 1414.6 mphNov 1414.6 mphApr 1414.6 mphApr 1414.6 mphNowNow
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction in Koshima varies throughout the year.

The wind is most often from the east for 1.6 months, from April 23 to June 10 and for 2.3 months, from July 30 to October 7, with a peak percentage of 42% on September 26. The wind is most often from the south for 1.6 months, from June 10 to July 30, with a peak percentage of 42% on July 2. The wind is most often from the north for 6.5 months, from October 7 to April 23, with a peak percentage of 61% on January 1.

Wind Direction in Koshima

Wind Direction in KoshimaNESENJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%NowNowwesteastnorthsouth
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

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 water temperature experiences some seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.0 months, from July 5 to October 4, with an average temperature above 80°F. The day of the year with the warmest water is August 14, with an average temperature of 83°F.

The time of year with cooler water lasts for 3.7 months, from December 26 to April 17, with an average temperature below 71°F. The day of the year with the coolest water is February 14, with an average temperature of 68°F.

Average Water Temperature in Koshima

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Best Time of Year to Visit

To characterize how pleasant the weather is in Koshima throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Koshima for general outdoor tourist activities is from late September to early November, with a peak score in the second week of October.

Tourism Score in Koshima

Tourism Score in Koshimabest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810107.37.32.32.35.65.63.93.9NowNowprecipitationprecipitationcloudscloudstemperaturetemperaturetourism score
The tourism score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Koshima for hot-weather activities is from mid July to early October, with a peak score in the last week of August.

Beach/Pool Score in Koshima

Beach/Pool Score in Koshimabest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.26.20.00.0NowNowprecipitationprecipitationcloudscloudstemperaturetemperature beach/pool score
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Growing Season

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.

Time Spent in Various Temperature Bands and the Growing Season in Koshima

Time Spent in Various Temperature Bands and the Growing Season in KoshimaJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%100%Jan 1100%Jan 1100%Jul 3100%Jul 3NowNowcoldcoolcomfortablewarmhotvery cold
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

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.

Growing Degree Days in Koshima

Growing Degree Days in KoshimaJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F1,000°F1,000°F2,000°F2,000°F3,000°F3,000°F4,000°F4,000°F5,000°F5,000°F6,000°F6,000°FJan 2090°FJan 2090°FApr 25900°FApr 25900°FJun 91,800°FJun 91,800°FDec 316,415°FDec 316,415°FNowNow
The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

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 experiences some seasonal variation over the course of the year.

The brighter period of the year lasts for 2.5 months, from June 27 to September 12, with an average daily incident shortwave energy per square meter above 5.2 kWh. The brightest day of the year is July 23, with an average of 5.7 kWh.

The darker period of the year lasts for 2.7 months, from November 11 to February 3, with an average daily incident shortwave energy per square meter below 3.4 kWh. The darkest day of the year is December 25, with an average of 2.9 kWh.

Average Daily Incident Shortwave Solar Energy in Koshima

Average Daily Incident Shortwave Solar Energy in KoshimabrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWhJul 235.7 kWhJul 235.7 kWhDec 252.9 kWhDec 252.9 kWhSep 125.2 kWhSep 125.2 kWhFeb 33.4 kWhFeb 33.4 kWhNowNow
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

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%).

Data Sources

This report illustrates the typical weather in Koshima, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There is only a single weather station, Yakushima Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of Koshima.

At a distance of 21 kilometers from Koshima, closer than our threshold of 150 kilometers, this station is deemed sufficiently nearby to be relied upon as our primary source for temperature and dew point records.

The station records are corrected for the elevation difference between the station and Koshima according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.

Please note that the station records themselves may additionally have been back-filled using other nearby stations or the MERRA-2 reanalysis.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for airports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.