Photo: kevin schuchmann · CC BY-SA 3.0Nights turn raw in Potosi each January, colder than in 92% of U.S. towns
The warmest part of a July day comes in at 83° on average. Expect the heaviest rain or snow in June and the lightest in January. Summers stay cool: July afternoons here are cooler than in 74% of U.S. towns. Comfortable outdoor weather lasts from May to September, with highs of 70–83°.
A year in Potosi at a glance
Each month’s typical high and low, and what it brings.
What stands out about Potosi’s climate
Compared with towns across the U.S., with Potosi’s place in Wisconsin beside it.
What a year in Potosi feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 166 frost-free days a year
In half of years the last 32° night comes by April 27 and the first by October 11. Frost and day counts come from NOAA’s station at Lancaster 4 Wsw, WI, 10 miles from the town’s center, 170 ft higher.
The 2023 USDA map puts Potosi’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 36 inches of snow a winter
Snow, measured at Dubuque L&d 11, IA, falls mostly in January. Precipitation (rain plus melted snow) adds up to 38 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 116 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Potosi
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 Lancaster 4 Wsw, WI.
Living with Potosi’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
166 frost-free days in zone 5a. The last frost comes by Apr 27 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 11.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 7.7 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Potosi from natural hazards, river flooding is the largest share (41%); heat waves, cold waves, winter storms and ice storms together are 20%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Potosi and its neighbors
Every town next door is within a degree of Potosi in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Potosi’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 |
|---|---|---|---|---|
| Potosi, WI | 11° | 83° | 38" | 36" |
| Boone, IA | 11° | 84° | 36" | 36" |
| Westville, IN | 16° | 83° | 39" | 34" |
| Colchester, VT | 10° | 81° | 38" | 50" |
| Hillsdale, MI | 16° | 82° | 38" | 44" |
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 Potosi averaged 0.8° warmer than the 1900s. The biggest change is in December (+2.1°).
A smaller shift than in 91% 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 Potosi compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Potosi’s place among Wisconsin’s.
Potosi weather by month
Highs, lows and precipitation from NOAA’s grid at Potosi’s center; snow, wet days and snow on the ground from Dubuque L&d 11, IA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 27° | 11° | 1.3" | 11.7" | 8 | 23 | 10° – 32° |
| February | 32° | 15° | 1.4" | 8.6" | 8 | 21 | 10° – 36° |
| March | 45° | 26° | 2.1" | 3.7" | 9 | 8 | 27° – 51° |
| April | 58° | 37° | 3.8" | 0.9" | 12 | 0 | 38° – 54° |
| May | 70° | 48° | 4.3" | 0.0" | 13 | 0 | 53° – 66° |
| June | 79° | 58° | 5.5" | 0.0" | 12 | 0 | 66° – 73° |
| July | 83° | 62° | 4.9" | 0.0" | 9 | 0 | 66° – 79° |
| August | 81° | 60° | 4.0" | 0.0" | 9 | 0 | 66° – 77° |
| September | 74° | 52° | 3.9" | 0.0" | 9 | 0 | 57° – 68° |
| October | 61° | 40° | 2.9" | 0.1" | 9 | 0 | 45° – 56° |
| November | 45° | 29° | 2.3" | 1.2" | 8 | 3 | 29° – 47° |
| December | 32° | 18° | 1.7" | 9.9" | 9 | 15 | 11° – 35° |
| Year | 57° | 38° | 38.0" | 36.1" | 116 | 71 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 10° to 36°. June is the most reliable, staying within 7°.
Where Potosi’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 Potosi’s center.
- Snow: Dubuque L&d 11, IA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Lancaster 4 Wsw, WI, 10 miles from the town’s center, 170 ft higher; 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 Potosi’s climate
What is the weather like in Potosi?
A typical July afternoon reaches 83°, a January night drops to 11°, and about 36 inches of snow falls in a normal winter. Colder January nights than 92% of U.S. towns; cooler July afternoons than 74% of U.S. towns.
How cold does it get in Potosi in winter?
January nights average 11°. About 150 nights a year reach 32° or below and 20 reach 0° or below. In the coldest January of the last 30 years the month averaged 10°.
How much snow does Potosi get?
About 36 inches in a normal winter at Dubuque L&d 11, IA, most of it in January, with snow on the ground about 71 days a year.
How hot does it get in Potosi?
July, with a typical high of 83° and a low of 62°. About 4 days a year reach 90° (Lancaster 4 Wsw, WI).
When is the first and last frost in Potosi?
In half of years the last spring frost (32°) comes by April 27 and the first fall frost by October 11, about 166 frost-free days, at Lancaster 4 Wsw, WI.
What growing zone is Potosi 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 Potosi?
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 Potosi getting warmer?
Yes: 1991–2020 averaged 0.8° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 91% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Potosi.
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.