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Weather extremes

How extreme does Janesville's weather get?

The hottest, coldest, wettest and snowiest days Janesville has recorded — the outer limits of what its weather can do, and how far they sit beyond a normal day.

Based on 50+ years of daily weather observations (1971–present), from the Beloit station 20 km away. Updated through June 2026 — an all-time extreme only changes when a more extreme day actually occurs, so some dates are old. That is normal, not stale data.

The four kinds of extreme

The hottest, coldest, wettest and snowiest single days Janesville has recorded — each shown against what a normal day that time of year looks like.

🔥 Hottest day
102°F Jul 16, 1988

That is about 22°F hotter than a normal July afternoon in Janesville (typical high near 80°F).

The three most extreme on record

1 102°F Jul 16, 1988
2 102°F Aug 18, 1988
3 101°F Jun 21, 1988
❄️ Coldest night
-29°F Jan 31, 2019

About 40°F colder than a normal January night in Janesville (typical low near 11°F).

The three most extreme on record

1 -29°F Jan 31, 2019
2 -28°F Feb 1, 2019
3 -27°F Jan 30, 2019
🌧️ Most rain in one day
5.77 in Jun 30, 1993

More rain in a single day than Janesville usually gets in the whole month of June (typical June total about 5.6 in).

The three most extreme on record

1 5.77 in Jun 30, 1993
2 5.00 in Aug 5, 1998
3 4.62 in Jun 16, 1997
Most snow in one day
15.0 in Feb 2, 2011

Close to a whole typical February's snow in one day (Janesville averages about 7 in across the month).

The three most extreme on record

1 15.0 in Feb 2, 2011
2 14.0 in Nov 21, 2015
3 11.0 in Dec 7, 1994

How hot and cold it gets, month by month

The shaded band is the normal range of daily temperatures for each month. The dots show the most extreme it has ever been — so you can see how far beyond a normal day the records really sit.

-50°-30°-10°10°30°50°70°90°110°130° all-time high 102°F JanFebMarAprMayJunJulAugSepOctNovDec
normal range of daily temperatureshottest ever recordedcoldest ever recorded

Janesville's record heat sits well above even a hot day for the season — July's 102°F is about 22°F beyond a normal hot afternoon. Its record cold is just as far below a normal winter night — the dots mark how rare each extreme really is.

In plain terms

In a normal year, Janesville's warmest days reach the low 80s°F and its coldest nights drop to the low 10s°F. But across the record it has gone as high as 102°F and as low as −29°F. A single day has delivered over 6 inches of rain or close to 15 inches of snow. Those are the outer edges worth knowing if you are moving here, planning a trip, or thinking about a house.
Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Madison Dane CO Rgnl AP (NOAA GHCN station USW00014837), about 57 km from the city centre.

How we build these numbers →