Average Weather in Saint Charles Illinois, United States
In Saint Charles, the summers are long, warm, 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 16°F to 83°F and is rarely below -3°F or above 91°F.
Based on the tourism score, the best time of year to visit Saint Charles for warm-weather activities is from mid June to mid September.
The warm season lasts for 3.9 months, from May 23 to September 20, with an average daily high temperature above 73°F. The hottest day of the year is July 19, with an average high of 83°F and low of 64°F.
The cold season lasts for 3.0 months, from December 1 to March 3, with an average daily high temperature below 41°F. The coldest day of the year is January 29, with an average low of 16°F and high of 30°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 Saint Charles, 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 Saint Charles begins around June 12 and lasts for 4.4 months, ending around October 26. On August 26, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 68% of the time, and overcast or mostly cloudy 32% of the time.
The cloudier part of the year begins around October 26 and lasts for 7.6 months, ending around June 12. 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 Saint Charles varies throughout the year.
The wetter season lasts 5.9 months, from March 30 to September 25, with a greater than 26% chance of a given day being a wet day. The chance of a wet day peaks at 38% on June 13.
The drier season lasts 6.1 months, from September 25 to March 30. The smallest chance of a wet day is 14% on February 2.
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 Saint Charles changes throughout the year.
Rain alone is the most common for 11 months, from February 4 to January 20. The highest chance of a day with rain alone is 38% on June 13.
Snow alone is the most common for 2.1 weeks, from January 20 to February 4. 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. Saint Charles experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Saint Charles. The most rain falls during the 31 days centered around June 3, with an average total accumulation of 3.8 inches.
The least rain falls around January 26, with an average total accumulation of 0.7 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. Saint Charles experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.4 months, from November 16 to March 30, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 9, with an average total liquid-equivalent accumulation of 0.4 inches.
The snowless period of the year lasts for 7.6 months, from March 30 to November 16. The least snow falls around July 21, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Saint Charles varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 7 minutes of daylight; the longest day is June 21, with 15 hours, 14 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:17 AM on June 15, and the latest sunrise is 2 hours, 11 minutes later at 7:28 AM on November 3. The earliest sunset is at 4:21 PM on December 8, and the latest sunset is 4 hours, 11 minutes later at 8:32 PM on June 27.
Daylight saving time (DST) is observed in Saint Charles during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.
Sunrise & Sunset with Twilight and Daylight Saving Time
Saint Charles experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.7 months, from May 30 to September 21, during which time the comfort level is muggy, oppressive, or miserable at least 11% of the time. The muggiest day of the year is July 22, with muggy conditions 43% of the time.
The least muggy day of the year is December 25, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
The average hourly wind speed in Saint Charles experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 7.7 months, from October 4 to May 27, with average wind speeds of more than 10.2 miles per hour. The windiest day of the year is March 24, with an average hourly wind speed of 12.6 miles per hour.
The calmer time of year lasts for 4.3 months, from May 27 to October 4. The calmest day of the year is August 3, with an average hourly wind speed of 7.7 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Saint Charles varies throughout the year.
The wind is most often from the north for 1.4 months, from March 5 to April 18, with a peak percentage of 29% on March 8. The wind is most often from the south for 2.3 months, from April 26 to July 3 and for 3.5 months, from July 29 to November 15, with a peak percentage of 36% on September 7. The wind is most often from the west for 3.7 weeks, from July 3 to July 29 and for 3.7 months, from November 15 to March 5, with a peak percentage of 32% on July 12.
Saint Charles 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 4 to September 25, with an average temperature above 65°F. The day of the year with the warmest water is August 11, with an average temperature of 72°F.
The time of year with cooler water lasts for 4.9 months, from December 12 to May 10, with an average temperature below 43°F. The day of the year with the coolest water is February 28, with an average temperature of 35°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Saint Charles 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 Saint Charles for general outdoor tourist activities is from mid June to mid September, with a peak score in the last week of August.
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 Saint Charles for hot-weather activities is from late June to late August, with a peak score in the third week of July.
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.
The growing season in Saint Charles typically lasts for 5.7 months (172 days), from around April 23 to around October 12, rarely starting before April 7 or after May 10, and rarely ending before September 24 or after October 30.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Saint Charles should appear around April 15, only rarely appearing before April 1 or after April 28.
Growing Degree Days
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 3.5 months, from May 5 to August 22, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is July 1, with an average of 6.9 kWh.
The darker period of the year lasts for 3.3 months, from November 2 to February 11, with an average daily incident shortwave energy per square meter below 2.7 kWh. The darkest day of the year is December 22, with an average of 1.7 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Saint Charles are 41.914 deg latitude, -88.309 deg longitude, and 755 ft elevation.
The topography within 2 miles of Saint Charles contains only modest variations in elevation, with a maximum elevation change of 161 feet and an average elevation above sea level of 747 feet. Within 10 miles also contains only modest variations in elevation (410 feet). Within 50 miles contains only modest variations in elevation (801 feet).
The area within 2 miles of Saint Charles is covered by artificial surfaces (87%) and trees (13%), within 10 miles by artificial surfaces (57%) and cropland (37%), and within 50 miles by cropland (54%) and artificial surfaces (28%).
This report illustrates the typical weather in Saint Charles, 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 Saint Charles.
For each station, the records are corrected for the elevation difference between that station and Saint Charles 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 Saint Charles is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Saint Charles and a given station.
The stations contributing to this reconstruction are: DuPage County Airport (85%, 5.2 kilometers, east); Chicago/Aurora Municipal Airport (10%, 21 kilometers, southwest); and DeKalb Taylor Municipal Airport (5%, 33 kilometers, west).
Time zones for aiports and weather stations are provided by AskGeo.com .