Lanark, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Lanark, a city in Carroll County, Illinois.
Tonight
63°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms between 11pm and 4am, then showers and thunderstorms likely. Some of the storms could produce heavy rain. Mostly cloudy. Low around 63, with temperatures rising to around 65 overnight. Southeast wind 10 to 15 mph. Chance of precipitation is 70%. New rainfall amounts between three quarters and one inch possible.
7-day forecast for Lanark
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 63°F | Chance Showers And Thunderstorms | 10 to 15 mph SE | 69% |
| Saturday | 78°F | Showers And Thunderstorms | 5 to 10 mph S | 86% |
| Saturday Night | 61°F | Showers And Thunderstorms Likely | 5 to 10 mph N | 74% |
| Sunday | 68°F | Rain Showers Likely | 10 to 15 mph NE | 74% |
| Sunday Night | 54°F | Rain Showers Likely | 15 to 20 mph NE | 55% |
| Monday | 64°F | Chance Rain Showers | 15 mph NE | 44% |
| Monday Night | 49°F | Chance Rain Showers | 10 to 20 mph NE | 44% |
| Tuesday | 62°F | Chance Rain Showers | 15 mph NE | 27% |
| Tuesday Night | 47°F | Partly Cloudy | 5 to 15 mph NE | 7% |
| Wednesday | 66°F | Mostly Sunny | 5 to 10 mph NE | 3% |
| Wednesday Night | 49°F | Partly Cloudy | 5 to 10 mph NE | 2% |
| Thursday | 67°F | Mostly Sunny | 5 mph NE | 4% |
| Thursday Night | 51°F | Partly Cloudy | 0 to 5 mph NE | 5% |
| Friday | 70°F | Mostly Sunny | 5 mph NE | 5% |
Forecast source: National Weather Service (api.weather.gov) for Lanark (42.102, -89.833). Updated through the day.
Growing snapshot for Lanark
Last spring frost
May 2
First fall frost
Oct 7
Growing season
154 days
Hardiness zone
5a
More local growing data for Lanark: nearby ZIP 61046 weather · frost dates · planting calendar · Illinois frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Mt Carroll, Il (8.8 mi from Lanark). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.