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Janesville, Wisconsin climate

Dfa Hot-summer humid continental

Janesville has a strongly seasonal cool-temperate climate (Hot-summer humid continental, Köppen Dfa). The hottest month is July with an average daily high near 82°F, while the coldest is January averaging around 12°F at night. Around 37 inches of precipitation falls each year, peaking in June (5.3 inches) and easing off in January (1.5 inches). Winters bring significant snowfall (52 inches of snow per year on average).

☀️ Summers

Warm

Highs near 82°F in July.

About 9 days a year above 90 °F

❄️ Winters

Very cold

Lows near 12°F in January.

About 147 freezing nights a year

🌧️ Rain & snow

Moderate rainfall

About 37 in of rain a year, plus 52 in of snow.

Snow falls through the winter months

⛅ Sky & trend

Partly cloudy

A roughly even mix of sun and cloud.

+1.1 °F vs 50 years ago

Temperature & precipitation

Daily high–low temperature range with the monthly average, plus monthly precipitation split into rain and snow · 1991–2020 normals · hover a month for the exact figures

Hours of sunshine per day

Estimated sunny hours each month — daylight length × clear-sky fraction · 1991–2020 monthly cloud cover (NASA POWER)

Janesville climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	27	31	44	57	69	79	82	80	73	60	45	32
Avg temp (°F)	19	23	34	46	58	68	72	70	62	50	37	25
Avg low (°F)	12	15	25	36	47	57	62	60	51	40	29	18
Precipitation (in)	1.5	1.5	2.3	3.8	4.1	5.3	4.5	4.2	3.4	2.8	2.2	1.6
Snowfall (in)	13.7	12.8	7.0	2.6	0.1	—	—	—	—	0.6	3.0	12.0

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°F)	27	31	44	57	69	79
Avg temp (°F)	19	23	34	46	58	68
Avg low (°F)	12	15	25	36	47	57
Precipitation (in)	1.5	1.5	2.3	3.8	4.1	5.3
Snowfall (in)	13.7	12.8	7.0	2.6	0.1	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	82	80	73	60	45	32
Avg temp (°F)	72	70	62	50	37	25
Avg low (°F)	62	60	51	40	29	18
Precipitation (in)	4.5	4.2	3.4	2.8	2.2	1.6
Snowfall (in)	—	—	—	0.6	3.0	12.0

How often — frequency of weather events

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	11	10	11	13	13	12	10	9	9	10	10	10
Days with high ≥ 90°F (days)	—	—	—	—	0.4	2	4	2	0.6	—	—	—
Days with low ≤ 32°F (days)	30	27	23	10	1	—	—	—	0.5	7	20	28
Days with snowfall ≥ 1 in (days)	4	4	2	0.8	0.0	—	—	—	—	0.2	1	3

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Days with measurable rain (days)	11	10	11	13	13	12
Days with high ≥ 90°F (days)	—	—	—	—	0.4	2
Days with low ≤ 32°F (days)	30	27	23	10	1	—
Days with snowfall ≥ 1 in (days)	4	4	2	0.8	0.0	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	10	9	9	10	10	10
Days with high ≥ 90°F (days)	4	2	0.6	—	—	—
Days with low ≤ 32°F (days)	—	—	0.5	7	20	28
Days with snowfall ≥ 1 in (days)	—	—	—	0.2	1	3

Sky & atmosphere

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	65	63	64	66	66	60	52	53	52	63	66	66
Relative humidity (%)	90	87	80	77	77	77	76	75	75	77	82	89
Wind speed (mph)	8.8	8.9	8.6	8.5	7.3	6.1	5.5	5.3	6.2	7.2	7.7	7.8

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Cloud cover (%)	65	63	64	66	66	60
Relative humidity (%)	90	87	80	77	77	77
Wind speed (mph)	8.8	8.9	8.6	8.5	7.3	6.1

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	52	53	52	63	66	66
Relative humidity (%)	76	75	75	77	82	89
Wind speed (mph)	5.5	5.3	6.2	7.2	7.7	7.8

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.

Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.

How we build these numbers →