Johnston, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Johnston, a city in Polk County, Iowa.
This Afternoon
66°F
Showers And Thunderstorms
Showers and thunderstorms. Cloudy. High near 66, with temperatures falling to around 61 in the afternoon. North wind around 7 mph. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast for Johnston
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 66°F | Showers And Thunderstorms | 7 mph N | 79% |
| Tonight | 46°F | Showers And Thunderstorms Likely | 8 to 12 mph NW | 72% |
| Wednesday | 52°F | Slight Chance Rain Showers | 15 mph W | 22% |
| Wednesday Night | 43°F | Mostly Cloudy then Chance Rain Showers | 12 mph W | 27% |
| Thursday | 52°F | Rain Showers Likely | 10 mph NW | 58% |
| Thursday Night | 41°F | Mostly Cloudy | 8 mph NNW | 9% |
| Friday | 52°F | Partly Sunny | 3 to 7 mph N | 3% |
| Friday Night | 35°F | Partly Cloudy | 0 to 3 mph N | 0% |
| Saturday | 57°F | Mostly Sunny | 0 to 3 mph WSW | 1% |
| Saturday Night | 38°F | Mostly Clear | 3 mph W | 4% |
| Sunday | 62°F | Sunny | 5 mph W | 6% |
| Sunday Night | 40°F | Mostly Clear | 5 mph SW | 1% |
| Monday | 65°F | Sunny | 5 to 9 mph SW | 0% |
| Monday Night | 42°F | Mostly Clear | 6 mph WNW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Johnston (41.692, -93.724). Updated through the day.
Growing snapshot for Johnston
Last spring frost
Apr 19
First fall frost
Oct 18
Growing season
179 days
Hardiness zone
5b
More local growing data for Johnston: nearby ZIP 50131 weather · frost dates · planting calendar · Iowa frost dates
Nearby towns & communities
Alleman
Altoona
Ankeny
Bondurant
Clive
Des Moines
Elkhart
Granger
Grimes
Maxwell
Mitchellville
Pleasant Hill
Polk City
Runnells
Saylorville
Sheldahl
Slater
Urbandale
West Des Moines
Windsor Heights
Climate data from the nearest NOAA station, Des Moines Wsfo-Johnston, Ia (2.8 mi from Johnston). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.