Janesville, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Janesville, a city in Bremer County, Iowa.
Overnight
65°F
Partly Cloudy
Partly cloudy, with a low around 65. South wind around 7 mph.
7-day forecast for Janesville
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 65°F | Partly Cloudy | 7 mph S | 4% |
| Tuesday | 77°F | Chance Showers And Thunderstorms | 7 to 10 mph W | 49% |
| Tuesday Night | 60°F | Showers And Thunderstorms Likely | 3 to 9 mph NNW | 66% |
| Wednesday | 73°F | Chance Showers And Thunderstorms then Partly Sunny | 5 mph NNE | 31% |
| Wednesday Night | 54°F | Mostly Clear | 1 to 5 mph N | 14% |
| Thursday | 78°F | Sunny | 1 to 5 mph E | 2% |
| Thursday Night | 59°F | Mostly Clear | 3 mph SSE | 0% |
| Friday | 81°F | Sunny | 2 to 10 mph SSE | 7% |
| Friday Night | 65°F | Mostly Clear | 8 mph S | 12% |
| Saturday | 84°F | Sunny | 5 to 9 mph S | 9% |
| Saturday Night | 69°F | Chance Showers And Thunderstorms | 9 to 13 mph S | 27% |
| Sunday | 85°F | Chance Showers And Thunderstorms | 12 mph SSE | 27% |
| Sunday Night | 69°F | Chance Showers And Thunderstorms | 7 to 10 mph SSE | 35% |
| Monday | 84°F | Chance Showers And Thunderstorms then Slight Chance Showers And Thunderstorms | 8 to 12 mph SSE | 35% |
Forecast source: National Weather Service (api.weather.gov) for Janesville (42.646, -92.462). Updated through the day.
Growing snapshot for Janesville
Last spring frost
Apr 27
First fall frost
Oct 10
Growing season
165 days
Hardiness zone
5a
More local growing data for Janesville: nearby ZIP 50647 weather · frost dates · planting calendar · Iowa frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Waterloo Muni Ap, Ia (8.3 mi from Janesville). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.