Johnston, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Johnston, a city in Polk County, Iowa.
Today
83°F
Showers And Thunderstorms Likely
Showers and thunderstorms likely. Partly sunny. High near 83, with temperatures falling to around 80 in the afternoon. Northwest wind 6 to 9 mph. Chance of precipitation is 70%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Johnston
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 83°F | Showers And Thunderstorms Likely | 6 to 9 mph NW | 73% |
| Tonight | 63°F | Showers And Thunderstorms | 6 to 9 mph NNE | 90% |
| Wednesday | 73°F | Showers And Thunderstorms Likely | 7 mph NE | 61% |
| Wednesday Night | 57°F | Chance Rain Showers | 1 to 5 mph NE | 26% |
| Thursday | 80°F | Sunny | 3 mph ENE | 3% |
| Thursday Night | 62°F | Mostly Clear | 3 mph SE | 3% |
| Friday | 85°F | Sunny | 2 to 7 mph S | 5% |
| Friday Night | 67°F | Mostly Clear | 6 mph SSE | 12% |
| Saturday | 89°F | Sunny | 2 to 9 mph S | 11% |
| Saturday Night | 72°F | Mostly Clear | 10 mph SSW | 11% |
| Sunday | 89°F | Mostly Sunny | 7 to 10 mph S | 11% |
| Sunday Night | 71°F | Slight Chance Showers And Thunderstorms | 9 mph SSE | 27% |
| Monday | 89°F | Chance Showers And Thunderstorms then Mostly Sunny | 8 to 13 mph S | 27% |
| Monday Night | 72°F | Slight Chance Showers And Thunderstorms | 8 to 13 mph ESE | 24% |
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 Aug 4, 2026.