Winter nights in Sumpter are colder than in 94% of U.S. towns
Expect July afternoons of about 83°. A year here swings 73° from midwinter lows to midsummer highs. Summers stay cool: July afternoons here are cooler than in 74% of U.S. towns. Picnics, hikes and garden evenings come into their own from May to September, with highs of 70–83°.
A year in Sumpter at a glance
Each month’s typical high and low, and what it brings.
What stands out about Sumpter’s climate
Compared with towns across the U.S., with Sumpter’s place in Wisconsin beside it.
What a year in Sumpter feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 152 frost-free days a year
In half of years the last 32° night comes by May 5 and the first by October 5. Frost and day counts come from NOAA’s station at Baraboo, WI, 7 miles from the town’s center, at about the same height.
The 2023 USDA map puts Sumpter’s center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −17°. 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 43 inches of snow a winter
Snow, measured at Baraboo, WI, falls mostly in January and December. Precipitation (rain plus melted snow) adds up to 37 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 119 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Sumpter
92% 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 Baraboo, WI.
Living with Sumpter’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
152 frost-free days in zone 5a. The last frost comes by May 5 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 5.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 37 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Sumpter from natural hazards, river flooding is the largest share (70%); heat waves, cold waves, winter storms and ice storms together are 13%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Sumpter and its neighbors
Every town next door is within a degree of Sumpter in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Sumpter’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 |
|---|---|---|---|---|
| Sumpter, WI | 10° | 83° | 37" | 43" |
| Mason City, IA | 8° | 82° | 36" | 44" |
| Colchester, VT | 10° | 81° | 38" | 50" |
| Red Wing, MN | 6° | 82° | 34" | 44" |
| Plattsburgh, NY | 9° | 81° | 35" | 50" |
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 Sumpter averaged 1.6° warmer than the 1900s. The biggest change is in December (+3.3°).
A bigger shift than in 66% 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 Sumpter compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Sumpter’s place among Wisconsin’s.
Sumpter weather by month
Highs, lows and precipitation from NOAA’s grid at Sumpter’s center; snow, wet days and snow on the ground from Baraboo, WI. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 27° | 10° | 1.3" | 11.3" | 8 | 22 | 7° – 31° |
| February | 32° | 13° | 1.4" | 10.1" | 7 | 23 | 10° – 34° |
| March | 44° | 24° | 2.1" | 5.9" | 9 | 11 | 26° – 50° |
| April | 58° | 35° | 3.8" | 2.6" | 11 | 2 | 37° – 52° |
| May | 70° | 47° | 4.2" | 0.0" | 13 | 0 | 52° – 65° |
| June | 79° | 57° | 5.3" | 0.0" | 12 | 0 | 65° – 72° |
| July | 83° | 61° | 4.4" | 0.0" | 10 | 0 | 65° – 78° |
| August | 81° | 59° | 4.3" | 0.0" | 10 | 0 | 65° – 75° |
| September | 73° | 50° | 3.6" | 0.0" | 10 | 0 | 55° – 67° |
| October | 60° | 38° | 2.8" | 0.4" | 10 | 0 | 44° – 55° |
| November | 45° | 28° | 2.2" | 2.1" | 8 | 3 | 28° – 46° |
| December | 33° | 17° | 1.7" | 10.3" | 9 | 15 | 11° – 36° |
| Year | 57° | 36° | 36.9" | 42.7" | 119 | 75 |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 7° to 31°. June is the most reliable, staying within 8°.
Where Sumpter’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 Sumpter’s center.
- Snow: Baraboo, WI.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Baraboo, WI, 7 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 Sumpter’s climate
What is the weather like in Sumpter?
A typical July afternoon reaches 83°, a January night drops to 10°, and about 43 inches of snow falls in a normal winter. Colder January nights than 94% of U.S. towns; cooler July afternoons than 74% of U.S. towns.
How cold does it get in Sumpter in winter?
January nights average 10°. About 169 nights a year reach 32° or below and 24 reach 0° or below. In the coldest January of the last 30 years the month averaged 7°.
How much snow does Sumpter get?
About 43 inches in a normal winter at Baraboo, WI, most of it in January and December, with snow on the ground about 75 days a year.
How hot does it get in Sumpter?
July, with a typical high of 83° and a low of 61°. About 11 days a year reach 90° (Baraboo, WI).
When is the first and last frost in Sumpter?
In half of years the last spring frost (32°) comes by May 5 and the first fall frost by October 5, about 152 frost-free days, at Baraboo, WI.
What growing zone is Sumpter in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −17°.
What is the best time of year to visit Sumpter?
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 Sumpter getting warmer?
Yes: 1991–2020 averaged 1.6° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 66% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Sumpter.
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.