Belvidere, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Belvidere, a city in Boone County, Illinois.
This Afternoon
68°F
Rain
Rain and a slight chance of thunderstorms. Cloudy. High near 68, with temperatures falling to around 66 in the afternoon. South wind 15 to 20 mph, with gusts as high as 35 mph. Chance of precipitation is 80%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Belvidere
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 68°F | Rain | 15 to 20 mph S | 81% |
| Tonight | 57°F | Rain | 15 mph S | 86% |
| Wednesday | 61°F | Chance Rain | 15 mph SSW | 50% |
| Wednesday Night | 46°F | Chance Rain | 15 mph SW | 31% |
| Thursday | 55°F | Chance Rain | 10 to 15 mph WSW | 51% |
| Thursday Night | 40°F | Chance Rain | 5 to 10 mph NW | 34% |
| Friday | 51°F | Slight Chance Rain then Mostly Cloudy | 10 mph N | 19% |
| Friday Night | 31°F | Partly Cloudy | 0 to 5 mph NNW | 2% |
| Saturday | 52°F | Mostly Sunny | 0 to 5 mph WNW | 2% |
| Saturday Night | 32°F | Partly Cloudy | 0 to 5 mph WSW | 3% |
| Sunday | 57°F | Mostly Sunny then Slight Chance Rain | 5 to 10 mph W | 16% |
| Sunday Night | 33°F | Mostly Clear | 0 to 5 mph W | 5% |
| Monday | 61°F | Sunny | 5 to 15 mph WSW | 2% |
| Monday Night | 37°F | Mostly Clear | 5 to 10 mph W | 1% |
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 Nov 3, 2026.