Janesville weather by month
Measured at Janesville/S Wisconsin Rgnl
Averages and records for each calendar month at Janesville/S Wisconsin Rgnl, United States, from 1987 to 2026. The warmest month is July, averaging 28.6°C; the coolest is January at −1.9°C.
| Month | Avg high | Avg low | Record high | Record low | Years |
|---|---|---|---|---|---|
| January | −1.9°C | −11.1°C | 15.6°C7 January 2008 | −34.4°C31 January 2019 | 38 / 39 |
| February | 0.4°C | −9.8°C | 23.3°C28 February 2024 | −35.0°C3 February 1996 | 37 / 39 |
| March | 7.4°C | −3.6°C | 28.3°C22 March 2012 | −24.4°C1 March 2015 | 39 / 39 |
| April | 14.5°C | 2.2°C | 31.7°C19 April 2002 | −9.4°C5 April 1995 | 39 / 39 |
| May | 21.3°C | 8.7°C | 35.6°C28 May 2018 | −2.8°C6 May 1989 | 39 / 39 |
| June | 26.9°C | 14.4°C | 38.3°C20 June 1988 | 2.2°C1 June 1993 | 38 / 39 |
| July | 28.6°C | 16.4°C | 39.4°C6 July 2012 | 7.2°C2 July 2001 | 38 / 39 |
| August | 27.7°C | 15.3°C | 38.9°C1 August 1988 | 6.1°C16 August 1992 | 40 / 40 |
| September | 24.1°C | 10.6°C | 35.6°C2 September 2000 | −2.2°C23 September 1995 | 40 / 40 |
| October | 16.6°C | 4.0°C | 31.7°C4 October 2025 | −10.0°C29 October 1988 | 39 / 39 |
| November | 8.1°C | −2.0°C | 24.4°C2 November 2016 | −20.0°C29 November 1995 | 37 / 38 |
| December | 0.8°C | −7.9°C | 19.4°C6 December 2001 | −31.7°C25 December 2000 | 38 / 39 |
Years shows the number behind the average high, then the number holding a record for that month. They differ because a year contributes an average only when the month has at least 25 days of readings, while a single reading is enough to set a record. The average low is withheld on the same 25-day rule and is counted separately again; it is shown as a dash where the archive cannot support it. Across the twelve months here the averages rest on 37 to 40 years each.
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Climate at nearby stations
The closest stations with twelve months of archive of their own, nearest first.
Every figure on this page is computed from NOAA GHCN-Daily observations stored per station, per year, per month. Nothing is modelled, interpolated or estimated, and a month the archive never covered is left out rather than filled in. A station appears here only once all twelve months carry an average from at least 10 years. See how this is built.