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Water temperature in Illinois Beach State Park (IL) in September

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Is it warm enough to swim in Illinois Beach State Park in September? Average water temperature in Illinois Beach State Park in September is 68°F and therefore suitable for comfortable swimming. The warmest water in Illinois Beach State Park in September is 74.1°F, and the coldest is 59.7°F. To find out the sea temperature today and in the coming days, go to Current sea temperature in Illinois Beach State Park

Changes water temperature in Illinois Beach State Park in September 2025, 2024

To get an accurate forecast for the water temperature in Illinois Beach State Park for any chosen month, compare two years within a 10 year range using the chart below. In addition to the sea water temperature in Illinois Beach State Park, the selected years in the table also show the values of the maximum and minimum temperatures on each of the days of September.

You can choose any other years:

Year 1:   Year 2:


Day 2025 2024 Min Max
September 171.4°F73.8°F64.9°F74.1°F
September 271.2°F73.4°F66°F73.4°F
September 371.2°F73.4°F64.8°F73.4°F
September 470°F73.4°F63.5°F73.4°F
September 569.3°F73.6°F63.3°F73.6°F
September 668.4°F73°F63°F73.4°F
September 767.3°F72°F64.8°F73°F
September 867.5°F70.7°F64.6°F72.1°F
September 966.4°F70.2°F63.7°F71.4°F
September 1067.1°F70.7°F64.2°F72.5°F
September 1168.2°F70.5°F65.5°F72.3°F
September 1268.5°F71.1°F65.8°F71.2°F
September 1368.9°F71.1°F64.4°F71.1°F
September 1469.3°F71.8°F64.4°F71.8°F
September 1570.2°F72.3°F63°F72.3°F
Day 2025 2024 Min Max
September 1670.3°F72.9°F62.6°F72.9°F
September 1770.5°F72.7°F63°F72.7°F
September 1870.9°F72.5°F63.1°F72.5°F
September 1971.6°F72.9°F63.1°F72.9°F
September 2070.9°F73.4°F63.1°F73.4°F
September 2171.1°F73.2°F62.2°F73.2°F
September 2270°F72.9°F61.5°F72.9°F
September 2369.1°F70.9°F61.7°F70.9°F
September 2469.8°F70.2°F61.5°F71.2°F
September 2569.3°F70.2°F61.7°F71.2°F
September 2669.4°F70.3°F62.1°F71.1°F
September 2769.1°F69.8°F61.9°F70.2°F
September 2869.4°F69.6°F60.6°F70°F
September 2969.6°F69.3°F59.7°F69.6°F
September 3069.8°F69.8°F60.8°F69.8°F
Illinois Beach State Park water temp chart in September

Average water temperature in Illinois Beach State Park in September over a decade

20162017201820192020
68.9°F68.5°F67.5°F64.6°F66.9°F
20212022202320242025
68.7°F68.4°F68.9°F71.8°F

Illinois Beach State Park sea state in September

Chart comparing the height of waves in Illinois Beach State Park in September over the past years. The red line indicates the height of the waves when swimming in the sea is prohibited. To view the current sea conditions, click on the graph.

Waves height in Illinois Beach State Park in September

Illinois Beach State Park water temperature during other months:

You can also view information about water temperature for other months by clicking on the month button below

Where is the warm sea water in September?

Want to know where the water temperature in September is good for swimming? Select the continent of interest, the day of the month and the required water temperature

Region
Date (day and month)
Water temperature: min 60°F
 Average temperature  Maximum temperature

Temperature in neighboring cities

The nearest locations with the average water temperature in September. In addition, the maximum and minimum water temperatures for that month, recorded over the last decade, are shown

AvrMinMax
Simmons Island Beach67.6°F61.3°F73.4°F
Tower Road Beach68°F53.2°F74.7°F
Glencoe68°F53.2°F74.7°F
Winnetka68.2°F55.9°F75°F
Wilmette68.4°F56.8°F75°F
Evanston68.7°F60.6°F75.4°F
Rogers Park68.7°F60.6°F75.4°F
Oak Creek66.4°F57.9°F73.6°F
Montrose Beach68.7°F61.7°F75°F
Foster Beach68.7°F61.7°F75°F

Illinois Beach State Park photo gallery

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[1] - The "Blue Flag" is awarded to beaches which fulfill a number of criteria, including: the quality of the bathing water, which must be in accordance with the relevant European Union Directive environmental education and information and beach area management and safety.

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Our report for Illinois Beach State Park is compiled using satellite data together with in-situ observations to get the most reliable daily data of sea surface temperatures, surf forecasts, current temperatures and weather forecasts.

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