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
90°F
Mostly Cloudy
Mostly cloudy, with a high near 90. Southwest wind around 7 mph.
7-day forecast for Lake Petersburg
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 90°F | Mostly Cloudy | 7 mph SW | 11% |
| Tonight | 69°F | Mostly Cloudy then Chance Showers And Thunderstorms | 2 to 6 mph SSW | 33% |
| Sunday | 81°F | Chance Showers And Thunderstorms | 2 to 10 mph N | 59% |
| Sunday Night | 60°F | Showers And Thunderstorms Likely then Chance Showers And Thunderstorms | 8 to 12 mph NE | 70% |
| Monday | 69°F | Showers And Thunderstorms Likely | 13 mph NE | 70% |
| Monday Night | 54°F | Chance Rain Showers | 12 mph NE | 46% |
| Tuesday | 66°F | Slight Chance Rain Showers | 12 mph NE | 24% |
| Tuesday Night | 51°F | Partly Cloudy | 5 to 10 mph NNE | 11% |
| Wednesday | 70°F | Mostly Sunny | 6 to 9 mph NNE | 2% |
| Wednesday Night | 53°F | Partly Cloudy | 3 to 8 mph NNE | 2% |
| Thursday | 71°F | Mostly Sunny | 3 to 7 mph NNE | 3% |
| Thursday Night | 55°F | Partly Cloudy | 2 to 7 mph NNE | 3% |
| Friday | 74°F | Mostly Sunny | 3 to 7 mph NE | 3% |
| Friday Night | 54°F | Partly Cloudy | 6 mph NE | 3% |
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 Sep 19, 2026.