Willow Reservoir, Wisconsin climate: Climate normals at a NOAA weather station
Willow Reservoir's normal year runs from 2°F January nights to 76°F July afternoons, with 32.3 inches of precipitation and 55 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 4.6°C, January lows of −17°C, July highs of 25°C, 819 mm of precipitation a year.
- NOAA stationWillow Reservoir
- Station IDUSC00479236
- Location45.71°N 89.85°W
- Elevation1,532 ft (467 m)
On October 23, the normal high in Willow Reservoir is 49°F and the normal low 33°F, and the chance of measurable rain or snow is 33%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Willow Reservoir.
- Jan 20° 2°
- Feb 25° 3°
- Mar 36° 14°
- Apr 49° 28°
- May 63° 41°
- Jun 72° 52°
- Jul 76° 57°
- Aug 75° 54°
- Sep 67° 46°
- Oct 53° 35°
- Nov 37° 23°
- Dec 25° 10°
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 Willow Reservoir each month?
July is the warmest month, with normal highs of 76°F; January the coldest, with normal lows of 2°F. The most precipitation falls in June (4.47 in), the least in February (1.00 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 20°F | 2°F | 11.1°F | 1.08 | 10.1 | 8 | <1 | 31 | 9 h |
| February | 25°F | 3°F | 14.0°F | 1.00 | 10.8 | 7 | <1 | 28 | 10 h 20 min |
| March | 36°F | 14°F | 25.0°F | 1.59 | 7.5 | 8 | <1 | 29 | 11 h 50 min |
| April | 49°F | 28°F | 38.4°F | 2.76 | 6.4 | 10 | <1 | 22 | 13 h 30 min |
| May | 63°F | 41°F | 52.3°F | 3.50 | 0.4 | 11 | <1 | 5 | 14 h 50 min |
| June | 72°F | 52°F | 62.2°F | 4.47 | 0.0 | 11 | <1 | <1 | 15 h 40 min |
| July | 76°F | 57°F | 66.5°F | 4.18 | 0.0 | 10 | 1 | <1 | 15 h 20 min |
| August | 75°F | 54°F | 64.4°F | 3.58 | 0.0 | 9 | <1 | <1 | 14 h 10 min |
| September | 67°F | 46°F | 56.6°F | 3.48 | 0.1 | 10 | <1 | 1 | 12 h 40 min |
| October | 53°F | 35°F | 44.0°F | 3.35 | 1.0 | 11 | <1 | 13 | 11 h |
| November | 37°F | 23°F | 30.2°F | 1.88 | 5.7 | 9 | <1 | 26 | 9 h 30 min |
| December | 25°F | 10°F | 17.8°F | 1.38 | 12.9 | 9 | <1 | 31 | 8 h 40 min |
| Year (annual) | 50°F | 31°F | 40.2°F | 32.25 | 54.9 | 111 | 1 | 185 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −6°C | −17°C | −11.6°C | 27 mm | 26 cm |
| February | −4°C | −16°C | −10.0°C | 25 mm | 27 cm |
| March | 2°C | −10°C | −3.9°C | 40 mm | 19 cm |
| April | 9°C | −2°C | 3.6°C | 70 mm | 16 cm |
| May | 17°C | 5°C | 11.3°C | 89 mm | 1 cm |
| June | 22°C | 11°C | 16.8°C | 114 mm | 0 cm |
| July | 25°C | 14°C | 19.2°C | 106 mm | 0 cm |
| August | 24°C | 12°C | 18.0°C | 91 mm | 0 cm |
| September | 19°C | 8°C | 13.7°C | 88 mm | 0 cm |
| October | 12°C | 2°C | 6.7°C | 85 mm | 3 cm |
| November | 3°C | −5°C | −1.0°C | 48 mm | 14 cm |
| December | −4°C | −12°C | −7.9°C | 35 mm | 33 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00479236; 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 Willow Reservoir?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, August has the fewest days with rain (9).
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 USC00479236.
When is the last frost at Willow Reservoir?
In Willow Reservoir, the last spring frost (32°F) comes after May 13 in half of years and after May 27 in one year in ten; the first autumn frost comes before October 3 in half of years and before September 16 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
- May 131 year in 10 after May 27; 9 in 10 after April 29
- First autumn frost, half of years before
- October 31 year in 10 before September 16; 9 in 10 before October 16
NOAA puts the median frost-free season at 141 days, and the season without a hard freeze (28°F) at 165 days.
A hard freeze (28°F) comes after May 2 in half of springs and before October 15 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Willow Reservoir in zone 4a in ZIP code 54531, 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 4a: the coldest night of a typical year reaches −25°F (24 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 USC00479236; 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 Willow Reservoir?
In a normal year in Willow Reservoir, 1 day a year reaches 90°F, 185 nights fall to 32°F or colder and 111 days bring measurable precipitation.
- Days at 90°F or more
- 1a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 185a normal year
- Days that stay below freezing
- 95high of 32°F or less
- Days with 0.01 inch of precipitation
- 111a normal year
- Days with 1 inch of snow or more
- 25a normal year
The highest temperature in this station's record (since 1934) is 112°F, on July 13, 1936; the lowest is −45°F, on January 18, 1982.
The wettest calendar year on that record is 1968, with 42.55 in; the snowiest season is 2022–23, with 104.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00479236; records: ACIS (NOAA Regional Climate Centers), station USC00479236. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Willow Reservoir?
Over a year 71% of the sunlight that would reach the ground under clear skies gets through the clouds at Willow Reservoir, 3.7 kWh per square metre a day. July is the sunniest month (78%) and December the cloudiest (56%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 65% | 1.6 |
| February | 73% | 2.6 |
| March | 73% | 3.8 |
| April | 68% | 4.6 |
| May | 69% | 5.4 |
| June | 72% | 6.0 |
| July | 78% | 6.1 |
| August | 76% | 5.1 |
| September | 73% | 3.9 |
| October | 65% | 2.5 |
| November | 61% | 1.5 |
| December | 56% | 1.1 |
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 Willow Reservoir record?
A normal year at Willow Reservoir brings 9,227 heating degree days, 72% more than the median U.S. place (5,373), and 232 cooling degree days, 74% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 1,767 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,669 | 0 |
| February | 1,429 | 0 |
| March | 1,240 | 0 |
| April | 798 | 0 |
| May | 403 | 9 |
| June | 130 | 47 |
| July | 51 | 96 |
| August | 81 | 61 |
| September | 270 | 18 |
| October | 650 | 1 |
| November | 1,043 | 0 |
| December | 1,463 | 0 |
| Year (annual) | 9,227 | 232 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00479236. 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 Willow Reservoir been warmer than normal?
2024 averaged 44.4°F, 4.2°F above the 1991-2020 normal of 40.2°F. 3 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 42.2°F | +2.0°F | 32.21 | 62.0 |
| 2022 | 39.2°F | −1.0°F | 27.09 | 62.6 |
| 2023 | 42.8°F | +2.6°F | 27.15 | 88.0 |
| 2024 | 44.4°F | +4.2°F | 29.37 | 38.8 |
Over 46 complete years from 1951 to 2024, the station's annual mean temperature rose at a fitted 3.4°F per century (+0.19°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00479236; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Willow Reservoir's climate compare?
Willow Reservoir is warmer than 4 of the 165 places with their own NOAA record in Wisconsin, and wetter than 31. Across the 7,247 U.S. stations with normals, its annual mean of 40.2°F is warmer than 6%.
In the Köppen classification computed from these normals, Willow Reservoir is Dfb: continental, no dry season, warm 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.
Questions about Willow Reservoir's climate
What is the coldest month at Willow Reservoir?
January, with a normal high of 20°F and a normal low of 2°F. The warmest is July (76°F by day, 57°F at night).
Does it snow at Willow Reservoir?
Yes: 55 inches in a normal year, falling on 31 days with 0.1 inch or more, the most in December (12.9 inches).
What is the rainiest month at Willow Reservoir?
June, with 4.47 in of precipitation in a normal year; the driest is February with 1.00 in.
What plant hardiness zone is Willow Reservoir in?
The USDA's 2023 map puts Willow Reservoir in zone 4a in ZIP code 54531, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −25°F (24 years, 1991-2020): zone 4a.
How late can frost come at Willow Reservoir?
In half of years the last 32°F night comes after May 13; in one year in ten it comes after May 27. Waiting until May 27 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Wisconsin climateThe statewide normals and every place in the state
- Rice Reservoir Tomahawk-2, WI13 miles from this station, 40.7°F a year
- Minocqua, WI14 miles from this station, 39.5°F a year
- Rhinelander, WI19 miles from this station, 41.4°F a year
- St Germain, WI22 miles from this station, 39.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made