Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
In Crystal Lake, entering September brings a subtle temperature decrement, reducing from August's moderately hot 78.1°F (25.6°C) to a pleasant 72.5°F (22.5°C). During the month of September, an average low-temperature of 55°F (12.8°C) is recorded.Humidity
The average relative humidity in September is 80%.Rainfall
In Crystal Lake, Illinois, during September, the rain falls for 12 days and regularly aggregates up to 1.46" (37mm) of precipitation. Throughout the year, there are 146.9 rainfall days, and 21.22" (539mm) of precipitation is accumulated.Snowfall
In Crystal Lake, snow does not fall in June through September.Daylight
In September, the average length of the day is 12h and 28min.On the first day of the month, sunrise is at 6:19 am and sunset at 7:26 pm. On the last day of September, sunrise is at 6:50 am and sunset at 6:35 pm CDT.
Sunshine
In Crystal Lake, the average sunshine in September is 8.8h.UV index
In Crystal Lake, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a medium vulnerability from unprotected exposure to Sun's UV rays for the average person.Note: In September, a regular UV index of 4 translates into these guidelines:
Ensure safety - Imperative it is to shield skin and eyes from damage. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. During bright days, sunglasses that offer UVA and UVB defense are recommended.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the average humidity in September?
How many days does it rain in September?
When it does not snow?
Does it snow in September?
What is the average length of the day in September?
When is the sunrise / sunset in September?
How many hours of sunshine does Crystal Lake have in September?
What is the UV index intensity in September?
Average temperature in September
Crystal Lake, IL
- Average high temperature in September: 72.5°F
The warmest month (with the highest average high temperature) is July (79.5°F).
The month with the lowest average high temperature is January (27°F).
- Average low temperature in September: 55°F
The month with the highest average low temperature is July (63.1°F).
The coldest month (with the lowest average low temperature) is January (15.1°F).
Average pressure in September
Crystal Lake, IL
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in September
Crystal Lake, IL
- Average wind speed in September: 7.1mph
The windiest months (with the highest average wind speed) are January and February (9.9mph).
The calmest month (with the lowest average wind speed) is August (6.2mph).
Average humidity in September
Crystal Lake, IL
- Average humidity in September: 80%
The months with the highest relative humidity are January and February (85%).
The months with the lowest relative humidity are April and October (76%).
Average rainfall in September
Crystal Lake, IL
- Average rainfall in September: 1.46"
The wettest month (with the highest rainfall) is June (2.8").
The driest months (with the least rainfall) are November and December (0.94").
Average rainfall days in September
Crystal Lake, IL
- Average rainfall days in September: 12 days
The month with the highest number of rainy days is July (18.5 days).
The month with the least rainy days is February (4.8 days).
Average snowfall in September
Crystal Lake, IL
- Average snowfall in September: 0"
The month with the highest snowfall is January (3.31").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Crystal Lake, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (12.5 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Crystal Lake, IL
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in September: 8h and 5min
The month with the most sunshine is July (Average sunshine: 10h and 0min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).
Average sunshine days in September
Crystal Lake, IL
- Average sunshine days in September: 14.2 days
The month with the most sunshine days is November (17.3 days).
The month with the least sunshine days is July (10 days).
Average UV index in September
Crystal Lake, IL
- Average UV index in September: 4
The month with the highest UV index is August (UV index 6).
The months with the lowest UV index are January and December (UV index 1).
Average cloud cover in September
Crystal Lake, IL
- Average cloud cover in September: 32
The month with the most cloud cover is January (Cloud cover 62).
The months with the least cloud cover are July and September (Cloud cover 32).
Average visibility in September
Crystal Lake, IL
- Average visibility in September: 6mi
The months with the highest visibility are March, April, May, June, July, September, October, November and December (6mi).
The months with the lowest visibility are January, February and August (5mi).
Crystal Lake, Illinois, USA
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