Johnston, IA Weather & Growing Conditions
Tonight
46°F
Chance Rain Showers
A chance of rain showers before 3am. Cloudy. Low around 46, with temperatures rising to around 48 overnight. West northwest wind around 13 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 46°F | Chance Rain Showers | 13 mph WNW | 40% |
| 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% |
| Tuesday | 64°F | Sunny | 5 mph NNW | 0% |
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 Nov 4, 2026.