Photo: Billwhittaker · CC BY-SA 3.0Nights turn raw in Shell Rock each January, colder than in 95% of U.S. towns
On a normal July day the thermometer tops out near 83°. The gap between a January night and a July afternoon is 74°. By precipitation alone, it ranks drier than 72% of U.S. towns. Picnics, hikes and garden evenings come into their own from May to September, with highs of 71–83°.
A year in Shell Rock at a glance
Each month’s typical high and low, and what it brings.
What stands out about Shell Rock’s climate
Compared with towns across the U.S., with Shell Rock’s place in Iowa beside it.
What a year in Shell Rock feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 165 frost-free days a year
In half of years the last 32° night comes by April 27 and the first by October 8. Frost and day counts come from NOAA’s station at Allison, IA, 11 miles from the town’s center, 130 ft higher.
The 2023 USDA map puts Shell Rock’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 39 inches of snow a winter
Snow, measured at Waterloo Muni Airport, 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 114 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Shell Rock
91% 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 Allison, IA.
Living with Shell Rock’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
165 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 8.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Shell Rock from natural hazards, river flooding is the largest share (59%); heat waves, cold waves, winter storms and ice storms together are 8%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Shell Rock and similar climates
TownRatings has no climate map of the towns around Shell Rock yet.
Climates most like Shell 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 |
|---|---|---|---|---|
| Shell Rock, IA | 9° | 83° | 37" | 39" |
| Portage, WI | 10° | 83° | 36" | 39" |
| Freeport, IL | 12° | 83° | 38" | 35" |
| Woodbury, MN | 7° | 82° | 33" | 40" |
| Colchester, VT | 10° | 81° | 38" | 50" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Shell Rock averaged 0.9° warmer than the 1900s. The biggest change is in December (+2.6°).
A smaller shift than in 85% 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 Shell Rock compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Shell Rock’s place among Iowa’s.
Shell Rock weather by month
Highs, lows and precipitation from NOAA’s grid at Shell Rock’s center; snow, wet days and snow on the ground from Waterloo Muni Airport. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 26° | 9° | 1.0" | 10.1" | 8 | 21 | 7° – 30° |
| February | 30° | 13° | 1.1" | 9.3" | 8 | 18 | 8° – 33° |
| March | 44° | 25° | 2.0" | 4.6" | 10 | 8 | 26° – 50° |
| April | 59° | 36° | 4.0" | 1.7" | 12 | 1 | 37° – 54° |
| May | 71° | 48° | 4.8" | 0.1" | 13 | 0 | 54° – 66° |
| June | 80° | 59° | 5.8" | 0.0" | 12 | 0 | 66° – 73° |
| July | 83° | 62° | 4.4" | 0.0" | 9 | 0 | 67° – 79° |
| August | 81° | 59° | 4.1" | 0.0" | 9 | 0 | 65° – 76° |
| September | 75° | 51° | 3.6" | 0.0" | 9 | 0 | 56° – 68° |
| October | 61° | 39° | 2.7" | 0.3" | 9 | 0 | 44° – 55° |
| November | 45° | 26° | 1.9" | 3.1" | 8 | 3 | 26° – 48° |
| December | 31° | 15° | 1.4" | 9.9" | 8 | 13 | 8° – 33° |
| Year | 57° | 37° | 36.7" | 39.1" | 114 | 64 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 8° to 33°. June is the most reliable, staying within 7°.
Where Shell 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 Shell Rock’s center.
- Snow: Waterloo Muni Airport.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Allison, IA, 11 miles from the town’s center, 130 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 Shell Rock’s climate
What is the weather like in Shell Rock?
A typical July afternoon reaches 83°, a January night drops to 9°, and about 39 inches of snow falls in a normal winter. Colder January nights than 95% of U.S. towns; cooler July afternoons than 72% of U.S. towns.
How cold does it get in Shell Rock in winter?
January nights average 9°. About 150 nights a year reach 32° or below and 21 reach 0° or below. In the coldest January of the last 30 years the month averaged 7°.
How much snow does Shell Rock get?
About 39 inches in a normal winter at Waterloo Muni Airport, most of it in January, February and December, with snow on the ground about 64 days a year.
How hot does it get in Shell Rock?
July, with a typical high of 83° and a low of 62°. About 12 days a year reach 90° (Allison, IA).
When is the first and last frost in Shell Rock?
In half of years the last spring frost (32°) comes by April 27 and the first fall frost by October 8, about 165 frost-free days, at Allison, IA.
What growing zone is Shell Rock 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 Shell 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 Shell Rock getting warmer?
Yes: 1991–2020 averaged 0.9° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 85% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Shell 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.