Belvidere, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Belvidere, a city in Boone County, Illinois.
Tonight
61°F
Chance Showers And Thunderstorms
A slight chance of rain showers before midnight, then a chance of showers and thunderstorms between midnight and 1am, then showers and thunderstorms likely. Some of the storms could produce heavy rain. Cloudy, with a low around 61. East southeast wind around 10 mph, with gusts as high as 20 mph. Chance of precipitation is 70%. New rainfall amounts between three quarters and one inch possible.
7-day forecast for Belvidere
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 61°F | Chance Showers And Thunderstorms | 10 mph ESE | 67% |
| Saturday | 76°F | Showers And Thunderstorms then Showers And Thunderstorms Likely | 5 to 10 mph ESE | 93% |
| Saturday Night | 62°F | Showers And Thunderstorms Likely then Showers And Thunderstorms | 5 to 10 mph NE | 77% |
| Sunday | 67°F | Showers And Thunderstorms Likely | 10 to 15 mph NE | 69% |
| Sunday Night | 53°F | Chance Rain Showers | 15 mph NE | 48% |
| Monday | 64°F | Chance Rain Showers | 15 mph ENE | 39% |
| Monday Night | 48°F | Chance Rain Showers | 10 to 15 mph NE | 39% |
| Tuesday | 63°F | Chance Rain Showers | 10 to 15 mph NE | 28% |
| Tuesday Night | 47°F | Mostly Cloudy | 5 to 10 mph NE | 11% |
| Wednesday | 66°F | Partly Sunny | 5 to 10 mph NE | 5% |
| Wednesday Night | 48°F | Partly Cloudy | 0 to 10 mph NNE | 4% |
| Thursday | 68°F | Partly Sunny | 0 to 5 mph NNE | 4% |
| Thursday Night | 49°F | Mostly Cloudy | 0 to 5 mph NE | 4% |
| Friday | 70°F | Mostly Sunny | 0 to 5 mph NNE | 5% |
Forecast source: National Weather Service (api.weather.gov) for Belvidere (42.265, -88.888). Updated through the day.
Growing snapshot for Belvidere
Last spring frost
Apr 28
First fall frost
Oct 12
Growing season
166 days
Hardiness zone
5b
More local growing data for Belvidere: nearby ZIP 61008 weather · frost dates · planting calendar · Illinois frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Marengo, Il (11.9 mi from Belvidere). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.