Johnston City, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Johnston City, a city in Williamson County, Illinois.
Today
65°F
Mostly Cloudy
Mostly cloudy. High near 65, with temperatures falling to around 63 in the afternoon. West wind 5 to 10 mph.
7-day forecast for Johnston City
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 65°F | Mostly Cloudy | 5 to 10 mph W | 4% |
| Tonight | 44°F | Mostly Clear | 3 mph WSW | 0% |
| Thursday | 69°F | Sunny | 3 to 8 mph WSW | 0% |
| Thursday Night | 45°F | Partly Cloudy | 2 mph WNW | 1% |
| Friday | 61°F | Partly Sunny | 3 to 12 mph NNW | 0% |
| Friday Night | 36°F | Partly Cloudy | 2 to 8 mph N | 0% |
| Saturday | 58°F | Mostly Sunny | 2 to 6 mph N | 0% |
| Saturday Night | 33°F | Partly Cloudy | 1 mph NNW | 0% |
| Sunday | 62°F | Sunny | 0 to 7 mph NW | 0% |
| Sunday Night | 34°F | Clear | 2 mph NNW | 1% |
| Monday | 66°F | Sunny | 0 to 7 mph WSW | 0% |
| Monday Night | 38°F | Clear | 2 mph SW | 1% |
| Tuesday | 70°F | Sunny | 1 to 6 mph WSW | 1% |
| Tuesday Night | 41°F | Mostly Clear | 1 mph NW | 1% |
Forecast source: National Weather Service (api.weather.gov) for Johnston City (37.821, -88.929). Updated through the day.
Growing snapshot for Johnston City
Last spring frost
Apr 4
First fall frost
Oct 28
Growing season
206 days
Hardiness zone
7a
More local growing data for Johnston City: nearby ZIP 62951 weather · frost dates · planting calendar · Illinois frost dates
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Climate data from the nearest NOAA station, Benton 2 N, Il (14.4 mi from Johnston City). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.