Photo: Awkwafaba · CC BY-SA 3.0Sussex has colder winter nights than 91% of U.S. towns
Peak summer warmth arrives in July, with afternoons near 82°. In July, afternoons here are cooler than in 84% of U.S. towns. December has warmed most since 1901–2000, part of a 1.4° rise. Garden planting can start around April 30; autumn frost returns near October 14.
A year in Sussex at a glance
Each month’s typical high and low, and what it brings.
What stands out about Sussex’s climate
Compared with towns across the U.S., with Sussex’s place in Wisconsin beside it.
What a year in Sussex feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 164 frost-free days a year
In half of years the last 32° night comes by April 30 and the first by October 14. Day counts come from NOAA’s station at Richfield 3 Ssw, WI, 5 miles from the town’s center, at about the same height; frost dates and degree days from Brookfield Wwtp, WI, 6 miles away.
The 2023 USDA map puts Sussex’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −14°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 54 inches of snow a winter
Snow, measured at Germantown, WI, is heaviest from January through February, about 16 inches a month. Precipitation (rain plus melted snow) adds up to 35 inches a year; June is the wettest month and February the driest. Rain or snow falls on about 125 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Sussex
93% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Brookfield Wwtp, WI.
Living with Sussex’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
164 frost-free days in zone 5b. The last frost comes by Apr 30 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 14.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 1.1 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Sussex from natural hazards, river flooding is the largest share (48%); heat waves, cold waves, winter storms and ice storms together are 28%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Sussex and its neighbors
Every town next door is within a degree of Sussex in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Sussex’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Sussex, WI | 12° | 82° | 35" | 54" |
| Plattsburgh, NY | 9° | 81° | 35" | 50" |
| Colchester, VT | 10° | 81° | 38" | 50" |
| Houghton Lake, MI | 12° | 81° | 33" | 66" |
| Hanover, NH | 9° | 82° | 39" | 61" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Sussex averaged 1.4° warmer than the 1900s. The biggest change is in December (+3.1°).
A smaller shift than in 50% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Sussex compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Sussex’s place among Wisconsin’s.
Sussex weather by month
Highs, lows and precipitation from NOAA’s grid at Sussex’s center; snow, wet days and snow on the ground from Germantown, WI. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 28° | 12° | 1.6" | 16.5" | 10 | 23 | 10° – 32° |
| February | 32° | 15° | 1.5" | 16.0" | 8 | 19 | 12° – 34° |
| March | 43° | 24° | 2.0" | 6.5" | 9 | 9 | 25° – 48° |
| April | 55° | 34° | 3.7" | 2.0" | 11 | 1 | 36° – 51° |
| May | 68° | 45° | 3.9" | 0.3" | 13 | 0 | 51° – 62° |
| June | 77° | 55° | 4.7" | 0.0" | 12 | 0 | 63° – 71° |
| July | 82° | 60° | 3.8" | 0.0" | 11 | 0 | 66° – 78° |
| August | 80° | 59° | 3.9" | 0.0" | 11 | 0 | 64° – 75° |
| September | 73° | 51° | 3.3" | 0.0" | 10 | 0 | 55° – 66° |
| October | 60° | 39° | 2.8" | 0.3" | 12 | 0 | 45° – 56° |
| November | 45° | 29° | 2.1" | 2.4" | 10 | 3 | 28° – 46° |
| December | 33° | 18° | 1.8" | 10.3" | 9 | 15 | 13° – 36° |
| Year | 56° | 37° | 35.0" | 54.3" | 125 | 70 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 13° to 36°. June is the most reliable, staying within 9°.
Where Sussex’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Sussex’s center.
- Snow: Germantown, WI.
- Frost dates, heating and cooling: Brookfield Wwtp, WI, 6 miles away.
- Freezing nights, 90° and 100° days: Richfield 3 Ssw, WI, 5 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Sussex’s climate
What is the weather like in Sussex?
A typical July afternoon reaches 82°, a January night drops to 12°, and about 54 inches of snow falls in a normal winter. Colder January nights than 91% of U.S. towns; cooler July afternoons than 84% of U.S. towns.
How cold does it get in Sussex in winter?
January nights average 12°. About 153 nights a year reach 32° or below and 17 reach 0° or below. In the coldest January of the last 30 years the month averaged 10°.
How much snow does Sussex get?
About 54 inches in a normal winter at Germantown, WI, heaviest from January through February, about 16 inches a month, with snow on the ground about 70 days a year.
How hot does it get in Sussex?
July, with a typical high of 82° and a low of 60°. About 13 days a year reach 90° (Brookfield Wwtp, WI).
When is the first and last frost in Sussex?
In half of years the last spring frost (32°) comes by April 30 and the first fall frost by October 14, about 164 frost-free days, at Brookfield Wwtp, WI.
What growing zone is Sussex in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −14°.
What is the best time of year to visit Sussex?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Sussex getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 50% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Sussex.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.