Below is the likelihood of experiencing 32°F on or before the given date in fall and on or after the given date in spring.
Links to high-population counties are below, and all counties are listed alphabetically.
These dates represent a freeze event. Gardeners often use the terms frost and freeze interchangeably. While they are similar (at least in what they do to our gardens), they are not the same.
A frost occurs when moisture in the air condenses and freezes. It is essentially when dew freezes. A freeze occurs when the air temperature drops below freezing. You can have a freeze without frost and you can have frost when air temperatures don't drop below freezing. Both can be destructive to plants (although a freeze tends to do more damage than a frost). Learn more in this article from Michigan State University: What is the Difference Between a Frost and Freeze?
Quick Links to Populous Counties
Polk Des Moines, West Des Moines, Ankeny, Urbandale, Johnston, Altoona, Clive
Linn Cedar Rapids, Marion
Scott Davenport, Bettendorf
Johnson Iowa City, Coralville, North Liberty
Black Hawk Waterloo, Cedar Falls
Woodbury Sioux City
Dallas Waukee, West Des Moines, Urbandale, Clive, Grimes
Dubuque Dubuque
Story Ames
Pottawattamie Council Bluffs
Warren Indianola, Norwalk
Clinton Clinton
Muscatine Muscatine
Cerro Gordo Mason City
Marshall Marshalltown
Freeze Dates by Iowa County
Adair | Adams | Allamakee | Appanoose | Audubon | Benton | Black Hawk | Boone | Bremer | Buchanan | Buena Vista | Butler | Calhoun | Carroll | Cass | Cedar | Cerro Gordo | Cherokee | Chickasaw | Clarke | Clay | Clayton | Clinton | Crawford | Dallas | Davis | Decatur | Delaware | Des Moines | Dickinson | Dubuque | Emmet | Fayette | Floyd | Franklin | Fremont | Greene | Grundy | Guthrie | Hamilton | Hancock | Hardin | Harrison | Henry | Howard | Humboldt | Ida | Iowa | Jackson | Jasper | Jefferson | Johnson | Jones | Keokuk | Kossuth | Lee | Linn | Louisa | Lucas | Lyon | Madison | Mahaska | Marion | Marshall | Mills | Mitchell | Monona | Monroe | Montgomery | Muscatine | O'Brien | Osceola | Page | Palo Alto | Plymouth | Pocahontas | Polk | Pottawattamie | Poweshiek | Ringgold | Sac | Scott | Shelby | Sioux | Story | Tama | Taylor | Union | Van Buren | Wapello | Warren | Washington | Wayne | Webster | Winnebago | Winneshiek | Woodbury | Worth | Wright
More Information
Data Source
This information is based on weather data collected from 1950-2021 provided by the Midwestern Regional Climate Center (MRCC). Visit that website to get more detailed information and statistics.