Illinois City, IL Weather & Growing Conditions

Local forecast, frost dates, hardiness zone and planting guidance for Illinois City, a community in Rock Island County, Illinois.

Overnight

52°F

Mostly Cloudy

Mostly cloudy. Low around 52, with temperatures rising to around 54 overnight. Southwest wind 10 to 15 mph, with gusts as high as 25 mph.

7-day forecast for Illinois City

When	Temp	Forecast	Wind	Precip
Overnight	52°F	Mostly Cloudy	10 to 15 mph SW	7%
Wednesday	54°F	Chance Rain Showers then Mostly Cloudy	15 mph SW	25%
Wednesday Night	46°F	Mostly Cloudy	10 to 15 mph SW	12%
Thursday	55°F	Rain Showers Likely	10 to 15 mph W	61%
Thursday Night	41°F	Slight Chance Rain Showers then Mostly Cloudy	10 mph N	16%
Friday	50°F	Partly Sunny	5 to 10 mph N	6%
Friday Night	32°F	Partly Cloudy	0 to 5 mph N	0%
Saturday	52°F	Sunny	0 to 5 mph NW	0%
Saturday Night	35°F	Mostly Clear	0 to 5 mph W	1%
Sunday	57°F	Sunny	5 to 10 mph W	1%
Sunday Night	36°F	Clear	0 to 5 mph W	1%
Monday	63°F	Sunny	0 to 10 mph SW	0%
Monday Night	41°F	Mostly Clear	5 mph W	0%
Tuesday	64°F	Sunny	5 mph NW	0%

Forecast source: National Weather Service (api.weather.gov) for Illinois City (41.399, -90.900). Updated through the day.

Growing snapshot for Illinois City

Last spring frost

Apr 18

First fall frost

Oct 24

Growing season

188 days

Hardiness zone

More local growing data for Illinois City: nearby ZIP 61259 weather · frost dates · planting calendar · Illinois frost dates

Nearby towns & communities

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Climate data from the nearest NOAA station, Illinois City Dam 16, Il (5.2 mi from Illinois City). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.