September Weather in Crystal Lake Illinois, United StatesDaily high temperatures decrease by 11°F, from 78°F to 67°F, rarely falling below 55°F or exceeding 87°F. Daily low temperatures decrease by 11°F, from 59°F to 47°F, rarely falling below 36°F or exceeding 68°F. For reference, on July 18, the hottest day of the year, temperatures in Crystal Lake typically range from 64°F to 83°F, while on January 22, the coldest day of the year, they range from 15°F to 29°F. The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. 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. Garrni, Armenia (6,040 miles away) is the far-away foreign place with temperatures most similar to Crystal Lake (view comparison). CloudsThe month of September in Crystal Lake experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 35% throughout the month. The clearest day of the month is September 14, with clear, mostly clear, or partly cloudy conditions 68% of the time. For reference, on December 30, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 58%, while on August 25, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 68%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Crystal Lake, the chance of a wet day over the course of September is decreasing, starting the month at 30% and ending it at 25%. For reference, the year's highest daily chance of a wet day is 38% on May 23, and its lowest chance is 14% on February 2. RainfallTo show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day. The average sliding 31-day rainfall during September in Crystal Lake is decreasing, starting the month at 3.3 inches, when it rarely exceeds 5.9 inches or falls below 1.2 inches, and ending the month at 2.8 inches, when it rarely exceeds 4.7 inches or falls below 1.1 inches. SunOver the course of September in Crystal Lake, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 21 minutes, implying an average daily decrease of 2 minutes, 48 seconds, and weekly decrease of 19 minutes, 37 seconds. The shortest day of the month is September 30, with 11 hours, 46 minutes of daylight and the longest day is September 1, with 13 hours, 7 minutes of daylight. The earliest sunrise of the month in Crystal Lake is 6:19 AM on September 1 and the latest sunrise is 31 minutes later at 6:49 AM on September 30. The latest sunset is 7:26 PM on September 1 and the earliest sunset is 51 minutes earlier at 6:35 PM on September 30. Daylight saving time is observed in Crystal Lake during 2024, but it neither starts nor ends during September, so the entire month is in daylight saving time. For reference, on June 20, the longest day of the year, the Sun rises at 5:16 AM and sets 15 hours, 16 minutes later, at 8:33 PM, while on December 21, the shortest day of the year, it rises at 7:19 AM and sets 9 hours, 5 minutes later, at 4:24 PM. The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation. MoonThe figure below presents a compact representation of key lunar data for September 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. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
HumidityWe 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. The chance that a given day will be muggy in Crystal Lake is very rapidly decreasing during September, falling from 25% to 4% over the course of the month. For reference, on July 21, the muggiest day of the year, there are muggy conditions 40% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time. WindThis 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 Crystal Lake is increasing during September, increasing from 8.6 miles per hour to 10.2 miles per hour over the course of the month. For reference, on January 15, the windiest day of the year, the daily average wind speed is 12.7 miles per hour, while on August 2, the calmest day of the year, the daily average wind speed is 7.9 miles per hour. The hourly average wind direction in Crystal Lake throughout September is predominantly from the south, with a peak proportion of 36% on September 5. Water TemperatureCrystal 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 surface water temperature in Crystal Lake is rapidly decreasing during September, falling by 8°F, from 70°F to 62°F, over the course of the month. Growing SeasonDefinitions 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 in Crystal Lake typically lasts for 5.5 months (168 days), from around April 26 to around October 11, rarely starting before April 8 or after May 14, and rarely ending before September 23 or after October 28. The month of September in Crystal Lake is more likely than not fully within the growing season, with the chance that a given day is in the growing season rapidly decreasing from 100% to 77% over the course of the month. 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. The average accumulated growing degree days in Crystal Lake are increasing during September, increasing by 383°F, from 2,372°F to 2,756°F, over the course of the month. Solar EnergyThis 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 in Crystal Lake is decreasing during September, falling by 1.3 kWh, from 5.5 kWh to 4.2 kWh, over the course of the month. TopographyFor the purposes of this report, the geographical coordinates of Crystal Lake are 42.241 deg latitude, -88.316 deg longitude, and 912 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%). Data SourcesThis 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 PointThere 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:
To get a sense of how much these sources agree with each other, you can view a comparison of Crystal Lake and the stations that contribute to our estimates of its temperature history and climate. Please note that each source's contribution is adjusted for elevation and the relative change present in the MERRA-2 data. Other DataAll data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , 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 airports and weather stations are provided by AskGeo.com . Maps are © OpenStreetMap contributors. DisclaimerThe information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site. We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands. We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader. Please review our full terms contained on our Terms of Service page. |