Climate and Average Weather Year Round at Iruma Ab Japan

At Iruma Ab, the summers are short, warm, oppressive, 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 95°F.

Based on the beach/pool score, the best time of year to visit Iruma Ab for hot-weather activities is from late July to late August.

The hot season lasts for 2.6 months, from June 26 to September 14, with an average daily high temperature above 79°F. The hottest month of the year at Iruma Ab is August, with an average high of 86°F and low of 73°F.

The cold season lasts for 3.5 months, from December 1 to March 17, with an average daily high temperature below 55°F. The coldest month of the year at Iruma Ab is January, with an average low of 31°F and high of 48°F.

At Iruma Ab, 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 Iruma Ab begins around October 6 and lasts for 5.8 months, ending around March 30.

The clearest month of the year at Iruma Ab is December, during which on average the sky is clear, mostly clear, or partly cloudy 74% of the time.

The cloudier part of the year begins around March 30 and lasts for 6.2 months, ending around October 6.

The cloudiest month of the year at Iruma Ab 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 at Iruma Ab varies significantly throughout the year.

The wetter season lasts 6.7 months, from March 22 to October 12, with a greater than 30% chance of a given day being a wet day. The month with the most wet days at Iruma Ab is June, with an average of 13.4 days with at least 0.04 inches of precipitation.

The drier season lasts 5.3 months, from October 12 to March 22. The month with the fewest wet days at Iruma Ab is December, with an average of 4.1 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 at Iruma Ab is June, with an average of 13.4 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 50% on June 23.

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. Iruma Ab experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year at Iruma Ab. The month with the most rain at Iruma Ab is September, with an average rainfall of 7.3 inches.

The month with the least rain at Iruma Ab is January, with an average rainfall of 1.4 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Iruma Ab experiences some seasonal variation in monthly snowfall.

The snowy period of the year lasts for 2.5 months, from December 28 to March 12, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow at Iruma Ab is February, with an average snowfall of 2.0 inches.

The snowless period of the year lasts for 9.5 months, from March 12 to December 28. The least snow falls around July 30, with an average total accumulation of 0.0 inches.

The length of the day at Iruma Ab varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 44 minutes of daylight; the longest day is June 21, with 14 hours, 36 minutes of daylight.

The earliest sunrise is at 4:25 AM on June 13, and the latest sunrise is 2 hours, 28 minutes later at 6:53 AM on January 7. The earliest sunset is at 4:28 PM on December 5, and the latest sunset is 2 hours, 34 minutes later at 7:02 PM on June 29.

Daylight saving time (DST) is not observed at Iruma Ab 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.

Iruma Ab experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 3.5 months, from June 10 to September 27, during which time the comfort level is muggy, oppressive, or miserable at least 23% of the time. The month with the most muggy days at Iruma Ab is August, with 27.6 days that are muggy or worse.

The least muggy day of the year is February 13, when muggy conditions are essentially unheard of.

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 Iruma Ab experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 4.8 months, from December 22 to May 17, with average wind speeds of more than 7.3 miles per hour. The windiest month of the year at Iruma Ab is March, with an average hourly wind speed of 8.2 miles per hour.

The calmer time of year lasts for 7.2 months, from May 17 to December 22. The calmest month of the year at Iruma Ab is July, with an average hourly wind speed of 6.4 miles per hour.

The predominant average hourly wind direction at Iruma Ab varies throughout the year.

The wind is most often from the north for 3.0 months, from January 13 to April 14 and for 2.9 months, from September 16 to December 12, with a peak percentage of 50% on February 24. The wind is most often from the south for 4.7 months, from April 14 to September 6, with a peak percentage of 45% on July 23. The wind is most often from the west for 1.0 months, from December 12 to January 13, with a peak percentage of 45% on January 1.

Iruma Ab 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 13 to September 28, with an average temperature above 74°F. The month of the year at Iruma Ab with the warmest water is August, with an average temperature of 78°F.

The time of year with cooler water lasts for 4.0 months, from December 24 to April 24, with an average temperature below 61°F. The month of the year at Iruma Ab with the coolest water is February, with an average temperature of 57°F.

To characterize how pleasant the weather is at Iruma Ab 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 Iruma Ab 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 Iruma Ab for hot-weather activities is from late July to late August, 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 at Iruma Ab typically lasts for 8.5 months (260 days), from around March 20 to around December 5, rarely starting before March 2 or after April 7, and rarely ending before November 17 or after December 22.

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 Iruma Ab should appear around April 1, only rarely appearing before March 21 or after April 13.

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 11 to August 26, with an average daily incident shortwave energy per square meter above 5.3 kWh. The brightest month of the year at Iruma Ab is May, with an average of 5.9 kWh.

The darker period of the year lasts for 3.1 months, from October 31 to February 4, with an average daily incident shortwave energy per square meter below 3.3 kWh. The darkest month of the year at Iruma Ab is December, with an average of 2.6 kWh.

For the purposes of this report, the geographical coordinates of Iruma Ab are 35.842 deg latitude, 139.411 deg longitude, and 282 ft elevation.

The topography within 2 miles of Iruma Ab contains only modest variations in elevation, with a maximum elevation change of 322 feet and an average elevation above sea level of 258 feet. Within 10 miles contains only modest variations in elevation (1,532 feet). Within 50 miles contains very significant variations in elevation (10,764 feet).

The area within 2 miles of Iruma Ab is covered by artificial surfaces (60%), cropland (23%), and trees (12%), within 10 miles by artificial surfaces (40%) and cropland (29%), and within 50 miles by trees (42%) and cropland (27%).