Average Weather in May in Herrin Illinois, United States
Daily high temperatures increase by 8°F, from 73°F to 81°F, rarely falling below 62°F or exceeding 89°F.
Daily low temperatures increase by 9°F, from 53°F to 62°F, rarely falling below 42°F or exceeding 71°F.
For reference, on July 21, the hottest day of the year, temperatures in Herrin typically range from 70°F to 89°F, while on January 22, the coldest day of the year, they range from 27°F to 43°F.
Average High and Low Temperature in May
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on May. 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.
Average Hourly Temperature in May
The month of May in Herrin experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 47% throughout the month. The highest chance of overcast or mostly cloudy conditions is 49% on May 27.
The clearest day of the month is May 1, with clear, mostly clear, or partly cloudy conditions 54% of the time.
For reference, on December 25, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 53%, while on August 23, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 71%.
Cloud Cover Categories in May
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Herrin, the chance of a wet day over the course of May is essentially constant, remaining around 39% throughout.
For reference, the year's highest daily chance of a wet day is 41% on May 12, and its lowest chance is 19% on January 28.
Probability of Precipitation in May
The average sliding 31-day rainfall during May in Herrin is decreasing, starting the month at 4.6 inches, when it rarely exceeds 8.7 inches or falls below 1.6 inches, and ending the month at 3.9 inches, when it rarely exceeds 6.7 inches or falls below 1.4 inches.
The highest average 31-day accumulation is 4.6 inches on May 2.
Average Monthly Rainfall in May
Over the course of May in Herrin, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 49 minutes, implying an average daily increase of 1 minute, 39 seconds, and weekly increase of 11 minutes, 33 seconds.
The shortest day of the month is May 1, with 13 hours, 46 minutes of daylight and the longest day is May 31, with 14 hours, 35 minutes of daylight.
Hours of Daylight and Twilight in May
The latest sunrise of the month in Herrin is 6:00 AM on May 1 and the earliest sunrise is 24 minutes earlier at 5:36 AM on May 31.
The earliest sunset is 7:46 PM on May 1 and the latest sunset is 25 minutes later at 8:11 PM on May 31.
Daylight saving time is observed in Herrin during 2019, but it neither starts nor ends during May, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:34 AM and sets 14 hours, 47 minutes later, at 8:21 PM, while on December 22, the shortest day of the year, it rises at 7:08 AM and sets 9 hours, 33 minutes later, at 4:40 PM.
Sunrise & Sunset with Twilight in May
The chance that a given day will be muggy in Herrin is very rapidly increasing during May, rising from 7% to 38% over the course of the month.
For reference, on July 20, the muggiest day of the year, there are muggy conditions 78% of the time, while on January 11, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in May
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Herrin is decreasing during May, decreasing from 9.3 miles per hour to 7.7 miles per hour over the course of the month.
For reference, on April 1, the windiest day of the year, the daily average wind speed is 10.5 miles per hour, while on July 27, the calmest day of the year, the daily average wind speed is 5.9 miles per hour.
Average Wind Speed in May
Wind Direction in May
The growing season in Herrin typically lasts for 7.0 months (213 days), from around April 1 to around November 1, rarely starting before March 13 or after April 20, and rarely ending before October 13 or after November 20.
The month of May in Herrin is reliably fully within the growing season.
Time Spent in Various Temperature Bands and the Growing Season in May
The average accumulated growing degree days in Herrin are rapidly increasing during May, increasing by 515°F, from 486°F to 1,002°F, over the course of the month.
Growing Degree Days in May
The average daily incident shortwave solar energy in Herrin is essentially constant during May, remaining within 0.2 kWh of 6.3 kWh throughout.
Average Daily Incident Shortwave Solar Energy in May
For the purposes of this report, the geographical coordinates of Herrin are 37.803 deg latitude, -89.028 deg longitude, and 400 ft elevation.
The topography within 2 miles of Herrin contains only modest variations in elevation, with a maximum elevation change of 121 feet and an average elevation above sea level of 413 feet. Within 10 miles also contains only modest variations in elevation (223 feet). Within 50 miles contains only modest variations in elevation (915 feet).
The area within 2 miles of Herrin is covered by artificial surfaces (45%), cropland (40%), and trees (15%), within 10 miles by cropland (55%) and trees (24%), and within 50 miles by cropland (63%) and trees (31%).
This report illustrates the typical weather in Herrin year round, 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 are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Herrin.
For each station, the records are corrected for the elevation difference between that station and Herrin according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Herrin is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Herrin and a given station.
The stations contributing to this reconstruction are: Williamson County Regional Airport (81%, 6 kilometers, south); Southern Illinois Airport (16%, 20 kilometers, west); and Mount Vernon Airport (3.0%, 60 kilometers, north).
Time zones for aiports and weather stations are provided by AskGeo.com .