Afton - Janesville Wastewater Treatment Plant, Wisconsin climate: Climate normals at a NOAA weather station
Afton - Janesville Wastewater Treatment Plant's normal year runs from 12°F January nights to 83°F July afternoons, with 37.4 inches of precipitation and 37 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.8°C, January lows of −11°C, July highs of 29°C, 951 mm of precipitation a year.
- NOAA stationAfton - Janesville Wastewater Treatment Plant
- Station IDUSC00470045
- Location42.64°N 89.06°W
- Elevation762 ft (232 m)
On October 23, the normal high in Afton - Janesville Wastewater Treatment Plant is 58°F and the normal low 37°F, and the chance of measurable rain or snow is 32%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Afton - Janesville Wastewater Treatment Plant.
- Jan 28° 12°
- Feb 32° 15°
- Mar 45° 25°
- Apr 58° 36°
- May 70° 48°
- Jun 80° 58°
- Jul 83° 62°
- Aug 82° 60°
- Sep 75° 51°
- Oct 62° 40°
- Nov 46° 29°
- Dec 34° 18°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like at Afton - Janesville Wastewater Treatment Plant each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 12°F. The most precipitation falls in June (4.99 in), the least in February (1.61 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 28°F | 12°F | 19.9°F | 1.63 | 10.8 | 10 | <1 | 30 | 9 h 20 min |
| February | 32°F | 15°F | 23.5°F | 1.61 | 10.1 | 9 | <1 | 26 | 10 h 30 min |
| March | 45°F | 25°F | 35.0°F | 2.06 | 4.1 | 10 | <1 | 24 | 11 h 50 min |
| April | 58°F | 36°F | 47.0°F | 3.57 | 1.3 | 12 | <1 | 10 | 13 h 20 min |
| May | 70°F | 48°F | 58.9°F | 4.09 | 0.0 | 13 | 1 | 1 | 14 h 40 min |
| June | 80°F | 58°F | 68.9°F | 4.99 | 0.0 | 13 | 3 | <1 | 15 h 20 min |
| July | 83°F | 62°F | 72.6°F | 4.19 | 0.0 | 10 | 5 | <1 | 15 h |
| August | 82°F | 60°F | 70.6°F | 4.34 | 0.0 | 10 | 3 | <1 | 14 h |
| September | 75°F | 51°F | 63.0°F | 3.73 | 0.0 | 10 | 2 | <1 | 12 h 30 min |
| October | 62°F | 40°F | 50.6°F | 2.99 | 0.2 | 10 | <1 | 8 | 11 h 10 min |
| November | 46°F | 29°F | 37.4°F | 2.33 | 2.4 | 9 | <1 | 21 | 9 h 50 min |
| December | 34°F | 18°F | 25.8°F | 1.90 | 7.7 | 10 | <1 | 29 | 9 h |
| Year (annual) | 58°F | 38°F | 47.8°F | 37.43 | 36.6 | 127 | 13 | 148 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −2°C | −11°C | −6.7°C | 41 mm | 27 cm |
| February | 0°C | −10°C | −4.7°C | 41 mm | 26 cm |
| March | 7°C | −4°C | 1.7°C | 52 mm | 10 cm |
| April | 14°C | 2°C | 8.3°C | 91 mm | 3 cm |
| May | 21°C | 9°C | 14.9°C | 104 mm | 0 cm |
| June | 27°C | 14°C | 20.5°C | 127 mm | 0 cm |
| July | 29°C | 17°C | 22.6°C | 106 mm | 0 cm |
| August | 28°C | 15°C | 21.4°C | 110 mm | 0 cm |
| September | 24°C | 11°C | 17.2°C | 95 mm | 0 cm |
| October | 17°C | 4°C | 10.3°C | 76 mm | 1 cm |
| November | 8°C | −2°C | 3.0°C | 59 mm | 6 cm |
| December | 1°C | −8°C | −3.4°C | 48 mm | 20 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00470045; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
Which months are mildest at Afton - Janesville Wastewater Treatment Plant?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (10).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00470045.
When is the last frost at Afton - Janesville Wastewater Treatment Plant?
In Afton - Janesville Wastewater Treatment Plant, the last spring frost (32°F) comes after April 26 in half of years and after May 11 in one year in ten; the first autumn frost comes before October 15 in half of years and before October 1 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 261 year in 10 after May 11; 9 in 10 after April 13
- First autumn frost, half of years before
- October 151 year in 10 before October 1; 9 in 10 before October 27
NOAA puts the median frost-free season at 170 days, and the season without a hard freeze (28°F) at 193 days.
A hard freeze (28°F) comes after April 15 in half of springs and before October 26 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Afton - Janesville Wastewater Treatment Plant in zone 5b in ZIP code 53548, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 5b: the coldest night of a typical year reaches −15°F (28 complete years).
Frost dates for every NOAA station in Wisconsin · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00470045; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get at Afton - Janesville Wastewater Treatment Plant?
In a normal year in Afton - Janesville Wastewater Treatment Plant, 13 days a year reach 90°F, 148 nights fall to 32°F or colder and 127 days bring measurable precipitation.
- Days at 90°F or more
- 13a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 148a normal year
- Days that stay below freezing
- 55high of 32°F or less
- Days with 0.01 inch of precipitation
- 127a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in this station's record (since 1987) is 103°F, on July 7, 2012; the lowest is −31°F, on February 3, 1996.
The wettest calendar year on that record is 2019, with 49.89 in; the snowiest season is 2007–08, with 86.7 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00470045; records: ACIS (NOAA Regional Climate Centers), station USC00470045. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Afton - Janesville Wastewater Treatment Plant?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds at Afton - Janesville Wastewater Treatment Plant, 3.9 kWh per square metre a day. July is the sunniest month (80%) and December the cloudiest (61%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 66% | 1.8 |
| February | 70% | 2.8 |
| March | 69% | 3.8 |
| April | 68% | 4.7 |
| May | 71% | 5.5 |
| June | 76% | 6.2 |
| July | 80% | 6.3 |
| August | 79% | 5.5 |
| September | 78% | 4.4 |
| October | 70% | 2.9 |
| November | 67% | 1.9 |
| December | 61% | 1.4 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How many heating and cooling degree days does Afton - Janesville Wastewater Treatment Plant record?
A normal year at Afton - Janesville Wastewater Treatment Plant brings 6,947 heating degree days, 29% more than the median U.S. place (5,373), and 710 cooling degree days, 22% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,831 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,396 | 0 |
| February | 1,161 | 0 |
| March | 931 | 1 |
| April | 543 | 3 |
| May | 231 | 43 |
| June | 38 | 156 |
| July | 6 | 240 |
| August | 15 | 188 |
| September | 130 | 71 |
| October | 454 | 7 |
| November | 828 | 0 |
| December | 1,215 | 0 |
| Year (annual) | 6,947 | 710 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00470045. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Have recent years at Afton - Janesville Wastewater Treatment Plant been warmer than normal?
2025 averaged 48.6°F, 0.8°F above the 1991-2020 normal of 47.8°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 49.3°F | +1.5°F | 29.01 | 35.7 |
| 2022 | 47.1°F | −0.7°F | 35.43 | 32.2 |
| 2023 | 50.0°F | +2.2°F | 29.93 | 36.3 |
| 2024 | 51.2°F | +3.4°F | 43.30 | 29.3 |
| 2025 | 48.6°F | +0.8°F | 33.20 | 37.3 |
Over 30 complete years from 1990 to 2025, the station's annual mean temperature rose at a fitted 3.9°F per century (+0.22°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00470045; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Afton - Janesville Wastewater Treatment Plant's climate compare?
Afton - Janesville Wastewater Treatment Plant is warmer than 154 of the 165 places with their own NOAA record in Wisconsin, and wetter than 133. Across the 7,247 U.S. stations with normals, its annual mean of 47.8°F is warmer than 31%.
In the Köppen classification computed from these normals, Afton - Janesville Wastewater Treatment Plant is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Afton - Janesville Wastewater Treatment Plant share this climate record?
3 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Janesville, WIalso near: Clinton (12 mi, 47.0°F a year); Beloit (13 mi, 45.4°F a year)66,428 people · 4 mi NE
- Footville, WI899 people · 8 mi W
- Hanover, WI143 people · 5 mi W
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Afton - Janesville Wastewater Treatment Plant's climate
What is the coldest month at Afton - Janesville Wastewater Treatment Plant?
January, with a normal high of 28°F and a normal low of 12°F. The warmest is July (83°F by day, 62°F at night).
Does it snow at Afton - Janesville Wastewater Treatment Plant?
Yes: 37 inches in a normal year, falling on 22 days with 0.1 inch or more, the most in January (10.8 inches).
What is the rainiest month at Afton - Janesville Wastewater Treatment Plant?
June, with 4.99 in of precipitation in a normal year; the driest is February with 1.61 in.
What plant hardiness zone is Afton - Janesville Wastewater Treatment Plant in?
The USDA's 2023 map puts Afton - Janesville Wastewater Treatment Plant in zone 5b in ZIP code 53548, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −15°F (28 years, 1991-2020): zone 5b.
How late can frost come at Afton - Janesville Wastewater Treatment Plant?
In half of years the last 32°F night comes after April 26; in one year in ten it comes after May 11. Waiting until May 11 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Wisconsin climateThe statewide normals and every place in the state
- Beloit, WI9 miles from this station, 45.4°F a year
- Clinton, WI11 miles from this station, 47.0°F a year
- Brodhead, WI16 miles from this station, 47.2°F a year
- Stoughton, WI21 miles from this station, 46.6°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made