Climate and Average Weather Year Round in Ishii Japan

In Ishii, the summers are short, hot, oppressive, and mostly cloudy; the winters are very cold and mostly clear; and it is wet year round. Over the course of the year, the temperature typically varies from 36°F to 88°F and is rarely below 30°F or above 94°F.

Based on the tourism score, the best time of year to visit Ishii for warm-weather activities is from early September to mid October.

The hot season lasts for 2.9 months, from June 23 to September 19, with an average daily high temperature above 80°F. The hottest month of the year in Ishii is August, with an average high of 88°F and low of 75°F.

The cool season lasts for 3.4 months, from December 4 to March 17, with an average daily high temperature below 56°F. The coldest month of the year in Ishii is January, with an average low of 36°F and high of 48°F.

In Ishii, 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 Ishii begins around September 16 and lasts for 6.3 months, ending around March 25.

The clearest month of the year in Ishii is December, during which on average the sky is clear, mostly clear, or partly cloudy 76% of the time.

The cloudier part of the year begins around March 25 and lasts for 5.7 months, ending around September 16.

The cloudiest month of the year in Ishii is June, during which on average the sky is overcast or mostly cloudy 69% of the time.

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

The wetter season lasts 6.0 months, from April 3 to October 5, with a greater than 34% chance of a given day being a wet day. The month with the most wet days in Ishii is June, with an average of 14.1 days with at least 0.04 inches of precipitation.

The drier season lasts 6.0 months, from October 5 to April 3. The month with the fewest wet days in Ishii is January, with an average of 5.1 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Ishii is June, with an average of 14.1 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 54% on June 27.

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. Ishii experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in Ishii. The month with the most rain in Ishii is June, with an average rainfall of 8.5 inches.

The month with the least rain in Ishii is January, with an average rainfall of 1.8 inches.

The length of the day in Ishii varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 53 minutes of daylight; the longest day is June 21, with 14 hours, 26 minutes of daylight.

The earliest sunrise is at 4:50 AM on June 12, and the latest sunrise is 2 hours, 18 minutes later at 7:08 AM on January 8. The earliest sunset is at 4:52 PM on December 5, and the latest sunset is 2 hours, 25 minutes later at 7:17 PM on June 29.

Daylight saving time (DST) is not observed in Ishii during 2024.

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

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.

Ishii experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 4.0 months, from June 4 to October 2, during which time the comfort level is muggy, oppressive, or miserable at least 25% of the time. The month with the most muggy days in Ishii is August, with 29.3 days that are muggy or worse.

The month with the fewest muggy days in Ishii is January, with 0.0 days that are muggy or worse.

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 Ishii experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 5.1 months, from November 19 to April 21, with average wind speeds of more than 6.8 miles per hour. The windiest month of the year in Ishii is February, with an average hourly wind speed of 8.5 miles per hour.

The calmer time of year lasts for 6.9 months, from April 21 to November 19. The calmest month of the year in Ishii is July, with an average hourly wind speed of 5.1 miles per hour.

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

The wind is most often from the north for 2.6 months, from February 2 to April 20 and for 2.8 months, from September 5 to November 29, with a peak percentage of 55% on October 11. The wind is most often from the south for 4.5 months, from April 20 to September 5, with a peak percentage of 46% on July 22. The wind is most often from the west for 2.1 months, from November 29 to February 2, with a peak percentage of 52% on January 1.

Ishii 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 2.7 months, from July 13 to October 5, with an average temperature above 76°F. The month of the year in Ishii with the warmest water is August, with an average temperature of 80°F.

The time of year with cooler water lasts for 4.7 months, from December 14 to May 6, with an average temperature below 63°F. The month of the year in Ishii with the coolest water is February, with an average temperature of 59°F.

To characterize how pleasant the weather is in Ishii 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 Ishii for general outdoor tourist activities is from early September to mid October, with a peak score in the last 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 Ishii for hot-weather activities is from mid July to early September, with a peak score in the second week of August.

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.

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 in Ishii typically lasts for 9.9 months (301 days), from around February 28 to around December 25, rarely starting before February 3 or after March 19, and rarely ending before December 8 or after January 9.

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 in Ishii should appear around March 26, only rarely appearing before March 13 or after April 5.

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 29, with an average daily incident shortwave energy per square meter above 5.4 kWh. The brightest month of the year in Ishii is May, with an average of 6.0 kWh.

The darker period of the year lasts for 3.0 months, from November 7 to February 8, with an average daily incident shortwave energy per square meter below 3.4 kWh. The darkest month of the year in Ishii is December, with an average of 2.8 kWh.

For the purposes of this report, the geographical coordinates of Ishii are 34.068 deg latitude, 134.442 deg longitude, and 33 ft elevation.

The topography within 2 miles of Ishii contains significant variations in elevation, with a maximum elevation change of 659 feet and an average elevation above sea level of 110 feet. Within 10 miles contains significant variations in elevation (3,412 feet). Within 50 miles also contains extreme variations in elevation (6,421 feet).

The area within 2 miles of Ishii is covered by cropland (75%) and trees (23%), within 10 miles by trees (59%) and cropland (30%), and within 50 miles by water (60%) and trees (31%).