Lake Petersburg, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Lake Petersburg, a community in Menard County, Illinois.
Today
87°F
Sunny
Sunny, with a high near 87. South wind around 6 mph.
7-day forecast for Lake Petersburg
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 87°F | Sunny | 6 mph S | 0% |
| Tonight | 68°F | Partly Cloudy | 6 mph SSE | 3% |
| Wednesday | 87°F | Slight Chance Rain Showers then Chance Showers And Thunderstorms | 7 mph S | 26% |
| Wednesday Night | 67°F | Chance Showers And Thunderstorms then Showers And Thunderstorms | 5 mph SSE | 77% |
| Thursday | 82°F | Showers And Thunderstorms | 5 mph S | 77% |
| Thursday Night | 65°F | Slight Chance Showers And Thunderstorms | 3 mph SSE | 16% |
| Friday | 84°F | Mostly Sunny | 2 mph SSW | 11% |
| Friday Night | 66°F | Slight Chance Showers And Thunderstorms | 2 mph SSW | 20% |
| Saturday | 87°F | Slight Chance Showers And Thunderstorms then Mostly Sunny | 2 to 6 mph SSW | 20% |
| Saturday Night | 70°F | Mostly Clear | 3 to 8 mph S | 10% |
| Sunday | 89°F | Sunny | 8 to 12 mph SSW | 5% |
| Sunday Night | 72°F | Partly Cloudy | 10 mph S | 13% |
| Monday | 90°F | Mostly Sunny | 10 mph SSW | 13% |
| Monday Night | 72°F | Slight Chance Showers And Thunderstorms | 9 mph SSW | 25% |
Forecast source: National Weather Service (api.weather.gov) for Lake Petersburg (39.984, -89.856). Updated through the day.
Growing snapshot for Lake Petersburg
Last spring frost
Apr 13
First fall frost
Oct 21
Growing season
189 days
Hardiness zone
6a
More local growing data for Lake Petersburg: nearby ZIP 62675 weather · frost dates · planting calendar · Illinois frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Petersburg 1E, Il (1.9 mi from Lake Petersburg). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.