Grafton, Wisconsin climate: Normal weather by month, frost dates and records
Grafton's normal year runs from 17°F January nights to 81°F July afternoons, with 35.5 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.8°C, January lows of −8°C, July highs of 27°C, 902 mm of precipitation a year.
- NOAA stationGrafton Wastewater Treatment Plant
- Station IDUSC00473198
- Location43.31°N 87.96°W
- Elevation741 ft (226 m)
- From the centerunder 1 mile
- Population12,741
On October 14, the normal high in Grafton is 62°F and the normal low 43°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Grafton.
- Jan 30° 17°
- Feb 33° 19°
- Mar 43° 26°
- Apr 54° 36°
- May 66° 46°
- Jun 76° 56°
- Jul 81° 62°
- Aug 80° 61°
- Sep 73° 54°
- Oct 61° 43°
- Nov 46° 31°
- Dec 35° 21°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Grafton each month?
July is the warmest month, with normal highs of 81°F; January the coldest, with normal lows of 17°F. The most precipitation falls in June (4.50 in), the least in January (1.58 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 30°F | 17°F | 23.5°F | 1.58 | – | <1 | 29 | 9 h 20 min |
| February | 33°F | 19°F | 25.8°F | 1.73 | – | <1 | 26 | 10 h 30 min |
| March | 43°F | 26°F | 34.5°F | 2.07 | – | <1 | 22 | 11 h 50 min |
| April | 54°F | 36°F | 45.2°F | 3.94 | – | <1 | 8 | 13 h 20 min |
| May | 66°F | 46°F | 55.9°F | 3.99 | – | <1 | <1 | 14 h 40 min |
| June | 76°F | 56°F | 65.7°F | 4.50 | – | 1 | <1 | 15 h 20 min |
| July | 81°F | 62°F | 71.5°F | 3.61 | – | 3 | <1 | 15 h 10 min |
| August | 80°F | 61°F | 70.2°F | 3.77 | – | 2 | <1 | 14 h |
| September | 73°F | 54°F | 63.2°F | 3.18 | – | <1 | <1 | 12 h 30 min |
| October | 61°F | 43°F | 51.5°F | 2.98 | – | <1 | 4 | 11 h 10 min |
| November | 46°F | 31°F | 38.8°F | 2.15 | – | <1 | 17 | 9 h 40 min |
| December | 35°F | 21°F | 28.3°F | 2.01 | – | <1 | 27 | 9 h |
| Year (annual) | 56°F | 39°F | 47.9°F | 35.51 | – | 6 | 134 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −8°C | −4.7°C | 40 mm |
| February | 1°C | −7°C | −3.4°C | 44 mm |
| March | 6°C | −3°C | 1.4°C | 53 mm |
| April | 12°C | 2°C | 7.3°C | 100 mm |
| May | 19°C | 8°C | 13.3°C | 101 mm |
| June | 24°C | 13°C | 18.7°C | 114 mm |
| July | 27°C | 17°C | 21.9°C | 92 mm |
| August | 27°C | 16°C | 21.2°C | 96 mm |
| September | 23°C | 12°C | 17.3°C | 81 mm |
| October | 16°C | 6°C | 10.8°C | 76 mm |
| November | 8°C | 0°C | 3.8°C | 55 mm |
| December | 2°C | −6°C | −2.1°C | 51 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Port Washington (8 miles away), gets 42 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00473198; 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.
When is the best weather to visit Grafton?
Normal highs sit between 65°F and 85°F in May, June, July, August and September.
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 USC00473198.
When is the last frost in Grafton?
In Grafton, the last spring frost (32°F) comes after April 23 in half of years and after May 9 in one year in ten; the first autumn frost comes before October 24 in half of years and before October 8 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 231 year in 10 after May 9; 9 in 10 after April 10
- First autumn frost, half of years before
- October 241 year in 10 before October 8; 9 in 10 before November 5
NOAA puts the median frost-free season at 182 days, and the season without a hard freeze (28°F) at 205 days.
A hard freeze (28°F) comes after April 11 in half of springs and before November 2 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Grafton in zone 6a in ZIP code 53024.
Frost dates for every NOAA station in Wisconsin · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00473198; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 in Grafton?
In a normal year in Grafton, 6 days a year reach 90°F and 134 nights fall to 32°F or colder.
- Days at 90°F or more
- 6a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 134a normal year
- Days that stay below freezing
- 50high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00473198.
How sunny is Grafton?
Over a year 70% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Grafton, 3.7 kWh per square metre a day. July is the sunniest month (80%) and December the cloudiest (53%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 54% | 1.4 |
| February | 60% | 2.3 |
| March | 66% | 3.5 |
| April | 68% | 4.6 |
| May | 70% | 5.4 |
| June | 75% | 6.0 |
| July | 80% | 6.1 |
| August | 79% | 5.2 |
| September | 77% | 4.2 |
| October | 67% | 2.6 |
| November | 62% | 1.7 |
| December | 53% | 1.2 |
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 much heating and cooling does Grafton need?
A normal year in Grafton brings 6,775 heating degree days, 26% more than the median U.S. place (5,373), and 564 cooling degree days, 38% 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 2,586 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,286 | 0 |
| February | 1,097 | 0 |
| March | 944 | 0 |
| April | 596 | 1 |
| May | 297 | 17 |
| June | 67 | 89 |
| July | 10 | 213 |
| August | 16 | 178 |
| September | 116 | 62 |
| October | 421 | 4 |
| November | 786 | 0 |
| December | 1,138 | 0 |
| Year (annual) | 6,775 | 564 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00473198. 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.
Has Grafton been warmer than normal lately?
2025 averaged 47.6°F, 0.3°F below the 1991-2020 normal of 47.9°F. 2 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 48.9°F | +1.0°F | 30.55 |
| 2022 | 46.5°F | −1.4°F | 39.60 |
| 2024 | 50.6°F | +2.7°F | 39.45 |
| 2025 | 47.6°F | −0.3°F | 37.47 |
Source: observed years: ACIS, station USC00473198. A year counts only with all twelve months complete.
How does Grafton's climate compare?
Grafton is warmer than 154 of the other 164 places with their own NOAA record in Wisconsin, and wetter than 95. Across the 7,247 U.S. stations with normals, its annual mean of 47.9°F is warmer than 31%.
In the Köppen classification computed from these normals, Grafton 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.
Which places near Grafton 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.
- Cedarburg, WI13,011 people · 2 mi W
- Bayside, WI4,338 people · 9 mi S
- Thiensville, WI3,299 people · 5 mi S
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 Grafton's climate
What is the coldest month in Grafton?
January, with a normal high of 30°F and a normal low of 17°F. The warmest is July (81°F by day, 62°F at night).
Does it snow in Grafton?
Yes. NOAA publishes no 1991-2020 snowfall normal for Grafton's NOAA station; the nearest record that keeps one, Port Washington (8 miles away), records 42 inches of snow in a normal year.
What is the rainiest month in Grafton?
June, with 4.50 in of precipitation in a normal year; the driest is January with 1.58 in.
What plant hardiness zone is Grafton in?
The USDA's 2023 map puts Grafton in zone 6a in ZIP code 53024.
How late can frost come in Grafton?
In half of years the last 32°F night comes after April 23; in one year in ten it comes after May 9. Waiting until May 9 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Wisconsin climateThe statewide normals and every place in the state
- Saukville, WI5 miles from this station, 45.0°F a year
- Port Washington, WI7 miles from this station, 46.7°F a year
- Germantown, WI10 miles from this station, 45.8°F a year
- Jackson, WI11 miles from this station, 46.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made