Average Weather in Crystal Lake Illinois, United States
In Crystal Lake, the summers are warm and wet; the winters are freezing, dry, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 15°F to 83°F and is rarely below -6°F or above 91°F.
Based on the tourism score, the best time of year to visit Crystal Lake for warm-weather activities is from mid June to mid September.
The warm season lasts for 3.9 months, from May 24 to September 19, with an average daily high temperature above 72°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 39°F. The coldest day of the year is January 22, with an average low of 15°F and high of 29°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 Crystal Lake, 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 Crystal Lake begins around June 11 and lasts for 4.4 months, ending around October 25. 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 25 and lasts for 7.6 months, ending around June 11. On December 31, 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
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. The chance of wet days in Crystal Lake varies throughout the year.
The wetter season lasts 6.1 months, from March 30 to October 3, with a greater than 26% chance of a given day being a wet day. The chance of a wet day peaks at 38% on May 24.
The drier season lasts 5.9 months, from October 3 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 Crystal Lake changes throughout the year.
Rain alone is the most common for 11 months, from February 15 to January 2. The highest chance of a day with rain alone is 38% on May 24.
Snow alone is the most common for 1.4 months, from January 2 to February 15. The highest chance of a day with snow alone is 8% on January 18.
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. Crystal Lake experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Crystal Lake. The most rain falls during the 31 days centered around June 8, with an average total accumulation of 3.8 inches.
The least rain falls around January 24, with an average total accumulation of 0.6 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. Crystal Lake experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.7 months, from November 12 to April 3, 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 29, with an average total liquid-equivalent accumulation of 0.5 inches.
The snowless period of the year lasts for 7.3 months, from April 3 to November 12. The least snow falls around July 19, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Crystal Lake varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 5 minutes of daylight; the longest day is June 21, with 15 hours, 16 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:16 AM on June 15, and the latest sunrise is 2 hours, 13 minutes later at 7:28 AM on November 3. The earliest sunset is at 4:20 PM on December 8, and the latest sunset is 4 hours, 13 minutes later at 8:33 PM on June 26.
Daylight saving time (DST) is observed in Crystal Lake 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
Crystal Lake experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.7 months, from May 30 to September 20, during which time the comfort level is muggy, oppressive, or miserable at least 10% of the time. The muggiest day of the year is July 22, with muggy conditions 40% of the time.
The least muggy day of the year is February 15, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Crystal Lake experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 7.7 months, from October 3 to May 26, with average wind speeds of more than 10.3 miles per hour. The windiest day of the year is January 15, with an average hourly wind speed of 12.7 miles per hour.
The calmer time of year lasts for 4.3 months, from May 26 to October 3. The calmest day of the year is August 3, with an average hourly wind speed of 7.9 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Crystal Lake 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 30% on March 8. The wind is most often from the south for 2.2 months, from April 27 to July 1; for 2.4 months, from August 5 to October 16; and for 1.1 weeks, from November 5 to November 13, with a peak percentage of 36% on September 6. The wind is most often from the west for 1.1 months, from July 1 to August 5; for 2.9 weeks, from October 16 to November 5; and for 3.7 months, from November 13 to March 5, with a peak percentage of 34% on November 2.
Crystal Lake 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 2.6 months, from July 5 to September 25, with an average temperature above 65°F. The day of the year with the warmest water is August 13, with an average temperature of 72°F.
The time of year with cooler water lasts for 5.1 months, from December 10 to May 14, with an average temperature below 43°F. The day of the year with the coolest water is March 1, with an average temperature of 35°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Crystal Lake 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 Crystal Lake 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 Crystal Lake for hot-weather activities is from late June to mid 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 Crystal Lake typically lasts for 5.5 months (168 days), from around April 27 to around October 12, rarely starting before April 9 or after May 15, and rarely ending before September 24 or after October 29.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Crystal Lake should appear around April 17, only rarely appearing before April 4 or after May 1.
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 21, 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 7.0 kWh.
The darker period of the year lasts for 3.4 months, from November 1 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 1.6 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Crystal Lake are 42.241 deg latitude, -88.316 deg longitude, and 892 ft elevation.
The topography within 2 miles of Crystal Lake contains only modest variations in elevation, with a maximum elevation change of 135 feet and an average elevation above sea level of 901 feet. Within 10 miles also contains only modest variations in elevation (308 feet). Within 50 miles contains only modest variations in elevation (745 feet).
The area within 2 miles of Crystal Lake is covered by artificial surfaces (80%) and trees (11%), within 10 miles by cropland (41%) and artificial surfaces (36%), and within 50 miles by cropland (51%) and artificial surfaces (25%).
This report illustrates the typical weather in Crystal Lake, 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 6 weather stations near enough to contribute to our estimation of the temperature and dew point in Crystal Lake.
For each station, the records are corrected for the elevation difference between that station and Crystal Lake 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 Crystal Lake is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Crystal Lake and a given station.
The stations contributing to this reconstruction are: DuPage County Airport (22%, 37 kilometers, south); Chicago Executive Airport (22%, 37 kilometers, east); Waukegan Regional Airport (18%, 42 kilometers, northeast); DeKalb Taylor Municipal Airport (15%, 47 kilometers, southwest); Burlington Municipal Airport (14%, 50 kilometers, north); and Southern Wisconsin Regional Airport (8%, 72 kilometers, northwest).
Time zones for aiports and weather stations are provided by AskGeo.com .