How cold is Illinois water in fall? In October water temperature throughout Illinois is not yet warm enough for swimming and does not exceed 68°F. Based on average water temperature observations over the past ten years, the warmest water temperature in Illinois in October was 59.7°F (in South Shore Beach), and the coldest 57.4°F (in Lake Bluff). To find out the sea temperature today and in the coming days, go to Current sea temperature in Illinois
Illinois cities and resorts with the values of the average water temperature in October in recent years.
For more detailed information about water temperature, surf forecast, weather and time of sunrise and sunset in any specific area of your interest, just click on a city name. For ease of search, all places are also grouped by the first letter of the name.
To find out what the water temperature was in Illinois any day over a period of the last ten years, select the month