Johnston City, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Johnston City, a city in Williamson County, Illinois.
Tonight
72°F
Slight Chance Showers And Thunderstorms then Partly Cloudy
A slight chance of showers and thunderstorms before 10pm. Partly cloudy. Low around 72, with temperatures rising to around 74 overnight. South southeast wind around 2 mph. Chance of precipitation is 20%.
7-day forecast for Johnston City
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 72°F | Slight Chance Showers And Thunderstorms then Partly Cloudy | 2 mph SSE | 22% |
| Saturday | 99°F | Sunny | 2 to 8 mph SW | 4% |
| Saturday Night | 73°F | Partly Cloudy | 5 mph SSW | 2% |
| Sunday | 98°F | Sunny | 3 to 8 mph WSW | 7% |
| Sunday Night | 70°F | Mostly Cloudy then Slight Chance Showers And Thunderstorms | 5 mph N | 17% |
| Monday | 88°F | Chance Showers And Thunderstorms | 3 to 12 mph N | 45% |
| Monday Night | 62°F | Chance Showers And Thunderstorms | 6 to 12 mph NNE | 45% |
| Tuesday | 77°F | Slight Chance Showers And Thunderstorms then Partly Sunny | 8 to 13 mph N | 19% |
| Tuesday Night | 57°F | Partly Cloudy | 5 to 13 mph N | 7% |
| Wednesday | 77°F | Mostly Sunny | 6 to 10 mph N | 2% |
| Wednesday Night | 56°F | Partly Cloudy | 3 to 9 mph NNE | 2% |
| Thursday | 77°F | Mostly Sunny | 3 to 10 mph NNE | 2% |
| Thursday Night | 58°F | Partly Cloudy | 2 to 8 mph NNE | 2% |
| Friday | 77°F | Mostly Sunny | 5 to 10 mph NNE | 4% |
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
Nearby towns & communities
Blairsville
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Carterville
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Creal Springs
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Freeman Spur
Herrin
Hurst
Marion
Pittsburg
Spillertown
Whiteash
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 Sep 19, 2026.