Castle Rock’s winters are colder and snowier than most of the U.S.
A typical July afternoon reaches 82°, a January night drops to 10°, and about 41 inches of snow falls in a normal winter.
A year in Castle Rock at a glance
Each month’s typical high and low, and what it brings.
What stands out about Castle Rock’s climate
Compared with towns across the U.S., with Castle Rock’s place in Wisconsin beside it.
What a year in Castle Rock feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 155 frost-free days a year
In half of years the last 32° night comes by May 3 and the first by October 7. Frost and day counts come from NOAA’s station at Boscobel Airport, 11 miles from the town’s center, 260 ft lower.
The 2023 USDA map puts Castle Rock’s center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −19°. 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 41 inches of snow a winter
Snow, measured at Dodgeville Wwtp, WI, falls mostly in January, February 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 116 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Castle Rock
90% 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 Boscobel Airport.
Living with Castle Rock’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
155 frost-free days in zone 5a. The last frost comes by May 3 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 7.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 3.5 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Castle Rock from natural hazards, river flooding is the largest share (48%); heat waves, cold waves, winter storms and ice storms together are 20%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Castle Rock and its neighbors
Every town next door is within a degree of Castle Rock in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Castle Rock’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 |
|---|---|---|---|---|
| Castle Rock, WI | 10° | 82° | 37" | 41" |
| Colchester, VT | 10° | 81° | 38" | 50" |
| Faribault, MN | 6° | 82° | 35" | 43" |
| Fort Dodge, IA | 9° | 83° | 34" | 39" |
| 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 Castle Rock averaged 1.0° warmer than the 1900s. The biggest change is in December (+2.7°).
A smaller shift than in 75% 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 Castle Rock compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Castle Rock’s place among Wisconsin’s.
Castle Rock weather by month
Highs, lows and precipitation from NOAA’s grid at Castle Rock’s center; snow, wet days and snow on the ground from Dodgeville Wwtp, WI. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 27° | 10° | 1.2" | 10.3" | 9 | 26 | 8° – 31° |
| February | 32° | 14° | 1.3" | 10.6" | 8 | 24 | 10° – 35° |
| March | 44° | 25° | 2.1" | 5.9" | 9 | 11 | 26° – 50° |
| April | 58° | 35° | 3.8" | 1.5" | 12 | 1 | 37° – 52° |
| May | 69° | 47° | 4.4" | 0.0" | 13 | 0 | 52° – 65° |
| June | 79° | 57° | 5.5" | 0.0" | 12 | 0 | 64° – 72° |
| July | 82° | 61° | 4.6" | 0.0" | 10 | 0 | 65° – 78° |
| August | 80° | 59° | 4.0" | 0.0" | 9 | 0 | 64° – 76° |
| September | 73° | 51° | 3.7" | 0.0" | 9 | 0 | 56° – 67° |
| October | 60° | 39° | 2.7" | 0.6" | 10 | 0 | 45° – 56° |
| November | 45° | 28° | 2.2" | 1.9" | 8 | 3 | 28° – 46° |
| December | 32° | 16° | 1.5" | 10.3" | 9 | 17 | 10° – 35° |
| Year | 57° | 37° | 37.0" | 41.1" | 116 | 81 |
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 35°. June is the most reliable, staying within 8°.
Where Castle Rock’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 Castle Rock’s center.
- Snow: Dodgeville Wwtp, WI.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Boscobel Airport, 11 miles from the town’s center, 260 ft lower; 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 Castle Rock’s climate
What is the weather like in Castle Rock?
A typical July afternoon reaches 82°, a January night drops to 10°, and about 41 inches of snow falls in a normal winter. Colder January nights than 94% of U.S. towns; cooler July afternoons than 81% of U.S. towns.
How cold does it get in Castle Rock in winter?
January nights average 10°. About 152 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 8°.
How much snow does Castle Rock get?
About 41 inches in a normal winter at Dodgeville Wwtp, WI, most of it in January, February and December, with snow on the ground about 81 days a year.
How hot does it get in Castle Rock?
July, with a typical high of 82° and a low of 61°. About 19 days a year reach 90° (Boscobel Airport).
When is the first and last frost in Castle Rock?
In half of years the last spring frost (32°) comes by May 3 and the first fall frost by October 7, about 155 frost-free days, at Boscobel Airport.
What growing zone is Castle Rock in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −19°.
What is the best time of year to visit Castle Rock?
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 Castle Rock getting warmer?
Yes: 1991–2020 averaged 1.0° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 75% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Castle Rock.
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.