Average Weather in Bloomington Illinois, United States
In Bloomington, the summers are long, warm, humid, and wet; the winters are freezing and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 18°F to 85°F and is rarely below -0°F or above 92°F.
The warm season lasts for 4.2 months, from May 18 to September 24, with an average daily high temperature above 74°F. The hottest day of the year is July 19, with an average high of 85°F and low of 66°F.
The cold season lasts for 3.1 months, from November 30 to March 1, with an average daily high temperature below 43°F. The coldest day of the year is January 28, with an average low of 18°F and high of 33°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
In Bloomington, 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 in Bloomington begins around June 13 and lasts for 4.5 months, ending around October 28. On August 26, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 70% of the time, and overcast or mostly cloudy 30% of the time.
The cloudier part of the year begins around October 28 and lasts for 7.5 months, ending around June 13. On December 29, the cloudiest day of the year, the sky is overcast or mostly cloudy 58% of the time, and clear, mostly clear, or partly cloudy 42% 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 in Bloomington varies throughout the year.
The wetter season lasts 5.9 months, from March 27 to September 24, with a greater than 27% chance of a given day being a wet day. The chance of a wet day peaks at 39% on June 7.
The drier season lasts 6.1 months, from September 24 to March 27. The smallest chance of a wet day is 14% on January 28.
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 in Bloomington changes throughout the year.
Rain alone is the most common for 11 months, from February 3 to January 15. The highest chance of a day with rain alone is 39% on June 7.
Snow alone is the most common for 2.7 weeks, from January 15 to February 3. The highest chance of a day with snow alone is 7% on January 21.
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. Bloomington experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Bloomington. The most rain falls during the 31 days centered around June 1, with an average total accumulation of 3.9 inches.
The least rain falls around January 26, with an average total accumulation of 0.9 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Bloomington experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.6 months, from November 14 to April 2, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around December 24, with an average total liquid-equivalent accumulation of 0.5 inches.
The snowless period of the year lasts for 7.4 months, from April 2 to November 14. The least snow falls around July 22, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Bloomington varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 17 minutes of daylight; the longest day is June 20, with 15 hours, 4 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:24 AM on June 14, and the latest sunrise is 2 hours, 5 minutes later at 7:29 AM on November 4. The earliest sunset is at 4:29 PM on December 7, and the latest sunset is 4 hours, 1 minute later at 8:30 PM on June 27.
Daylight saving time (DST) is observed in Bloomington during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
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.
Bloomington experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.8 months, from May 27 to September 20, during which time the comfort level is muggy, oppressive, or miserable at least 15% of the time. The muggiest day of the year is July 22, with muggy conditions 57% of the time.
The least muggy day of the year is December 23, 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 in Bloomington experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 7.6 months, from October 8 to May 27, with average wind speeds of more than 5.4 miles per hour. The windiest day of the year is April 1, with an average hourly wind speed of 6.9 miles per hour.
The calmer time of year lasts for 4.4 months, from May 27 to October 8. The calmest day of the year is August 3, with an average hourly wind speed of 4.0 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Bloomington varies throughout the year.
The wind is most often from the north for 1.1 weeks, from March 7 to March 15, with a peak percentage of 28% on March 8. The wind is most often from the south for 8.6 months, from March 15 to December 2, with a peak percentage of 38% on November 10. The wind is most often from the west for 3.2 months, from December 2 to March 7, with a peak percentage of 38% on January 1.
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 extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 3.9 months, from April 30 to August 28, with an average daily incident shortwave energy per square meter above 5.8 kWh. The brightest day of the year is July 2, with an average of 6.9 kWh.
The darker period of the year lasts for 3.2 months, from November 4 to February 10, with an average daily incident shortwave energy per square meter below 2.8 kWh. The darkest day of the year is December 17, with an average of 1.8 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Bloomington are 40.484 deg latitude, -88.994 deg longitude, and 807 ft elevation.
The topography within 2 miles of Bloomington contains only modest variations in elevation, with a maximum elevation change of 138 feet and an average elevation above sea level of 794 feet. Within 10 miles also contains only modest variations in elevation (253 feet). Within 50 miles contains only modest variations in elevation (531 feet).
The area within 2 miles of Bloomington is covered by artificial surfaces (100%), within 10 miles by cropland (86%) and artificial surfaces (13%), and within 50 miles by cropland (91%).
This report illustrates the typical weather in Bloomington, 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 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Bloomington.
For each station, the records are corrected for the elevation difference between that station and Bloomington 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 Bloomington is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Bloomington and a given station.
The stations contributing to this reconstruction are: Central Illinois Regional Airport at Bloomington-Normal (95%, 3.7 kilometers, east); Logan County Airport (2.4%, 46 kilometers, southwest); General Downing - Peoria International Airport (1.6%, 62 kilometers, west); and Marshall County Airport (1.4%, 68 kilometers, northwest).
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.