Johnston, IA Weather & Growing Conditions
Today
81°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms before 10am, then a chance of showers and thunderstorms between 10am and noon, then a slight chance of showers and thunderstorms. Partly sunny. High near 81, with temperatures falling to around 78 in the afternoon. West wind 5 to 8 mph. Chance of precipitation is 50%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 81°F | Chance Showers And Thunderstorms | 5 to 8 mph W | 45% |
| Tonight | 62°F | Chance Showers And Thunderstorms | 8 mph N | 38% |
| Sunday | 66°F | Chance Rain Showers then Slight Chance Showers And Thunderstorms | 12 mph NNE | 38% |
| Sunday Night | 57°F | Showers And Thunderstorms Likely | 10 mph NE | 58% |
| Monday | 61°F | Rain Showers Likely | 12 mph NE | 55% |
| Monday Night | 52°F | Chance Rain Showers | 6 to 9 mph NE | 53% |
| Tuesday | 60°F | Partly Sunny | 8 mph ENE | 10% |
| Tuesday Night | 47°F | Partly Cloudy | 2 to 6 mph ENE | 2% |
| Wednesday | 65°F | Sunny | 5 mph ENE | 2% |
| Wednesday Night | 52°F | Partly Cloudy | 3 mph E | 5% |
| Thursday | 66°F | Slight Chance Rain Showers | 1 to 5 mph ESE | 22% |
| Thursday Night | 56°F | Mostly Cloudy | 3 mph ESE | 8% |
| Friday | 68°F | Partly Sunny | 2 to 6 mph ESE | 8% |
| Friday Night | 57°F | Mostly Cloudy | 5 mph ESE | 9% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Johnston, IA
Last spring frost
Apr 19
First fall frost
Oct 18
Growing season
179 days
Hardiness zone
5b
Explore more for Johnston, IA: full frost dates · planting calendar · Iowa frost dates
Climate data from the nearest NOAA station, Des Moines Wsfo-Johnston, Ia (2.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.