Average Weather at Yokota Air Base Japan
At Yokota Air Base, the summers are short, warm, muggy, wet, and mostly cloudy and the winters are very cold and mostly clear. Over the course of the year, the temperature typically varies from 30°F to 87°F and is rarely below 24°F or above 94°F.
Based on the tourism score, the best time of year to visit Yokota Air Base for warm-weather activities is from late July to early October.
The hot season lasts for 2.6 months, from June 27 to September 16, with an average daily high temperature above 79°F. The hottest day of the year is August 7, with an average high of 87°F and low of 73°F.
The cold season lasts for 3.5 months, from December 2 to March 19, with an average daily high temperature below 56°F. The coldest day of the year is January 20, with an average low of 30°F and high of 48°F.
Average High and Low Temperature
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
At Yokota Air Base, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year at Yokota Air Base begins around October 7 and lasts for 5.7 months, ending around March 31. On December 27, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 76% of the time, and overcast or mostly cloudy 24% of the time.
The cloudier part of the year begins around March 31 and lasts for 6.3 months, ending around October 7. On June 27, the cloudiest day of the year, the sky is overcast or mostly cloudy 73% of the time, and clear, mostly clear, or partly cloudy 27% of the time.
Cloud Cover Categories
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at Yokota Air Base varies significantly throughout the year.
The wetter season lasts 6.6 months, from March 23 to October 12, with a greater than 30% chance of a given day being a wet day. The chance of a wet day peaks at 50% on June 24.
The drier season lasts 5.4 months, from October 12 to March 23. The smallest chance of a wet day is 11% on December 30.
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 50% on June 24.
Daily Chance of Precipitation
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. Yokota Air Base experiences extreme seasonal variation in monthly rainfall.
Rain falls throughout the year at Yokota Air Base. The most rain falls during the 31 days centered around September 20, with an average total accumulation of 7.3 inches.
The least rain falls around January 1, with an average total accumulation of 1.4 inches.
Average Monthly Rainfall
The sliding 31-day liquid-equivalent quantity of snowfall at Yokota Air Base does not vary significantly over the course of the year, staying within 0.1 inches of 0.1 inches throughout.
Average Liquid-Equivalent Monthly Snowfall
The length of the day at Yokota Air Base varies significantly over the course of the year. In 2017, the shortest day is December 22, with 9 hours, 44 minutes of daylight; the longest day is June 21, with 14 hours, 35 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 4:26 AM on June 13, and the latest sunrise is 2 hours, 27 minutes later at 6:53 AM on January 7. The earliest sunset is at 4:28 PM on December 6, and the latest sunset is 2 hours, 34 minutes later at 7:02 PM on June 28.
Daylight saving time (DST) is not observed at Yokota Air Base during 2017.
Sunrise & Sunset with Twilight
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.
Yokota Air Base experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.5 months, from June 11 to September 27, during which time the comfort level is muggy, oppressive, or miserable at least 22% of the time. The muggiest day of the year is August 8, with muggy conditions 89% of the time.
The least muggy day of the year is February 11, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
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 at Yokota Air Base experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 4.8 months, from December 24 to May 18, with average wind speeds of more than 7.4 miles per hour. The windiest day of the year is March 25, with an average hourly wind speed of 8.4 miles per hour.
The calmer time of year lasts for 7.2 months, from May 18 to December 24. The calmest day of the year is August 1, with an average hourly wind speed of 6.4 miles per hour.
Average Wind Speed
The predominant average hourly wind direction at Yokota Air Base varies throughout the year.
The wind is most often from the south for 4.9 months, from April 16 to September 13, with a peak percentage of 46% on July 24. The wind is most often from the north for 3.3 months, from September 13 to December 22 and for 3.5 months, from December 31 to April 16, with a peak percentage of 47% on November 23. The wind is most often from the west for 1.3 weeks, from December 22 to December 31, with a peak percentage of 44% on December 30.
Yokota Air Base 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 significant seasonal variation over the course of the year.
The time of year with warmer water lasts for 2.5 months, from July 15 to September 29, with an average temperature above 74°F. The day of the year with the warmest water is August 19, with an average temperature of 79°F.
The time of year with cooler water lasts for 4.0 months, from December 26 to April 25, with an average temperature below 61°F. The day of the year with the coolest water is February 24, with an average temperature of 57°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is at Yokota Air Base 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 Yokota Air Base for general outdoor tourist activities is from late July to early October, with a peak score in the first week of September.
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 Yokota Air Base for hot-weather activities is from late July to early September, with a peak score in the second week of August.
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.
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).
The growing season at Yokota Air Base typically lasts for 8.6 months (262 days), from around March 21 to around December 8, rarely starting before March 2 or after April 7, and rarely ending before November 20 or after December 26.
Time Spent in Various Temperature Bands and 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.
Based on growing degree days alone, the first spring blooms at Yokota Air Base should appear around April 1, only rarely appearing before March 19 or after April 13.
Growing Degree Days
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 significant seasonal variation over the course of the year.
The brighter period of the year lasts for 4.5 months, from April 12 to August 28, with an average daily incident shortwave energy per square meter above 5.3 kWh. The brightest day of the year is May 23, with an average of 5.9 kWh.
The darker period of the year lasts for 3.1 months, from November 1 to February 4, with an average daily incident shortwave energy per square meter below 3.3 kWh. The darkest day of the year is December 20, with an average of 2.6 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Yokota Air Base are 35.748 deg latitude, 139.348 deg longitude, and 430 ft elevation.
The topography within 2 miles of Yokota Air Base contains only modest variations in elevation, with a maximum elevation change of 249 feet and an average elevation above sea level of 433 feet. Within 10 miles contains only modest variations in elevation (2,477 feet). Within 50 miles contains large variations in elevation (12,451 feet).
The area within 2 miles of Yokota Air Base is covered by artificial surfaces (46%), cropland (28%), and trees (17%), within 10 miles by artificial surfaces (40%) and trees (38%), and within 50 miles by trees (42%) and cropland (23%).
This report illustrates the typical weather at Yokota Air Base, 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
Yokota Air Base has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.
In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.
The stations on which we may fall back include but are not limited to Iruma Ab, Atsugi United States Naval Air Station, Tokyo, Tokyo International Airport, Yokosuka Fwf, Shimofusa Ab, Tateyama Ab, and Narita International Airport.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports 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.
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.