Janesville, IA Weather & Growing Conditions
Tonight
59°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms. Mostly cloudy. Low around 59, with temperatures rising to around 61 overnight. North northeast wind 9 to 13 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 | 59°F | Chance Showers And Thunderstorms | 9 to 13 mph NNE | 40% |
| Sunday | 66°F | Chance Rain Showers then Chance Drizzle | 16 mph NE | 33% |
| Sunday Night | 52°F | Slight Chance Drizzle then Chance Rain Showers | 14 mph ENE | 44% |
| Monday | 60°F | Rain Showers Likely | 15 mph NE | 65% |
| Monday Night | 48°F | Rain Showers Likely | 9 to 13 mph NE | 65% |
| Tuesday | 60°F | Chance Rain Showers then Partly Sunny | 8 to 12 mph ENE | 27% |
| Tuesday Night | 45°F | Partly Cloudy | 5 to 8 mph NE | 2% |
| Wednesday | 64°F | Mostly Sunny | 7 mph ENE | 1% |
| Wednesday Night | 49°F | Partly Cloudy | 5 mph E | 4% |
| Thursday | 66°F | Slight Chance Rain Showers | 5 mph ESE | 16% |
| Thursday Night | 54°F | Slight Chance Rain Showers | 3 mph ESE | 22% |
| Friday | 70°F | Slight Chance Rain Showers then Partly Sunny | 2 to 6 mph E | 15% |
| Friday Night | 55°F | Mostly Cloudy | 5 mph ESE | 8% |
| Saturday | 69°F | Slight Chance Rain Showers | 3 to 9 mph SE | 18% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Janesville, IA
Last spring frost
Apr 27
First fall frost
Oct 10
Growing season
165 days
Hardiness zone
5a
Explore more for Janesville, IA: full frost dates · planting calendar · Iowa frost dates
Climate data from the nearest NOAA station, Waterloo Muni Ap, Ia (8.3 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 20, 2026.