Iowa frost dates: Last spring and first autumn frost at every NOAA station, 1991-2020
Across Iowa's 150 NOAA stations with frost dates, the median last spring frost (32°F) runs from April 10 in Keokuk to May 8 in Elkader; for half of its places it comes after April 28.
- Typical last spring frost
- April 28median of 132 places
- Typical first autumn frost
- October 10median of 132 places
- Earliest last frost
- April 10Keokuk
- Latest last frost
- May 8Elkader
When is the last frost in Iowa, town by town?
Each date is NOAA's: "after April 28 in half of years" means the last 32°F night of spring came after April 28 in half of the years 1991-2020. By the 1-in-10 date, the last frost has passed in nine years out of ten.
Find your town in the list, or look up a ZIP code for the stations nearest it.
| Place or station | Last frost (median) | 1 in 10 after | First frost (median) | 1 in 10 before | Growing season | Zone |
|---|---|---|---|---|---|---|
| KeokukKeokuk Lock Dam 19 | April 10 | April 26 | October 27 | October 10 | 198 days | 6a |
| Fort Madison | April 12 | April 26 | October 25 | October 11 | 194 days | 6a |
| BurlingtonBurlington Municipal Airport | April 15 | May 1 | October 20 | October 6 | 187 days | 5b |
| Bloomfield | April 16 | April 30 | October 22 | October 5 | 188 days | 5b |
| LamoniLamoni Municipal Airport | April 16 | May 2 | October 21 | October 6 | 186 days | 5b |
| Lamoni station | April 16 | May 2 | October 20 | October 6 | 187 days | – |
| Le ClaireLe Claire Lock and Dam 14 | April 16 | April 30 | October 25 | October 11 | 190 days | 5b |
| Donnellson | April 17 | May 1 | October 22 | October 10 | 187 days | – |
| Lamoni station | April 17 | May 1 | October 21 | October 6 | 184 days | – |
| Burlington (2 mi S) | April 18 | May 3 | October 20 | October 6 | 185 days | 6a |
| Des MoinesDes Moines International Airport | April 18 | May 2 | October 20 | October 4 | 184 days | 5b |
| Muscatine (2 mi N) | April 18 | May 2 | October 22 | October 8 | 184 days | – |
| RathbunRathbun Dam | April 18 | May 2 | October 23 | October 10 | 187 days | – |
| Des Moines Weather Office-Johnston | April 19 | May 3 | October 18 | October 1 | 179 days | 5b |
| Dubuque Lock and Dam 11 | April 19 | May 4 | October 21 | October 7 | 184 days | 5a |
| Sidney1 mi SSE | April 19 | May 2 | October 19 | October 1 | 182 days | 6a |
| Knoxville | April 20 | May 4 | October 19 | October 1 | 180 days | – |
| Shenandoah | April 20 | May 3 | October 17 | October 1 | 179 days | 5b |
| Allerton | April 21 | May 6 | October 19 | October 3 | 178 days | – |
| Davenport Weather Office | April 21 | May 7 | October 17 | October 3 | 176 days | – |
| Des Moines (17 mi E) | April 21 | May 5 | October 15 | September 30 | 174 days | – |
| GuttenbergGuttenberg Lock and Dam 10 | April 21 | May 6 | October 18 | October 4 | 178 days | 5a |
| Iowa CityIowa City Municipal Airport | April 21 | May 6 | October 18 | October 4 | 180 days | 5b |
| Oskaloosa | April 21 | May 4 | October 16 | September 29 | 176 days | – |
| Tipton | April 21 | May 4 | October 15 | October 1 | 175 days | 5a |
| ClintonClinton #1 | April 22 | May 8 | October 16 | October 2 | 175 days | 5b |
| Newton | April 22 | May 4 | October 17 | October 1 | 174 days | 5b |
| Ames (8 mi WSW) | April 23 | May 5 | October 14 | September 29 | 173 days | – |
| Ankeny | April 23 | May 6 | October 15 | September 30 | 173 days | 5b |
| Beaconsfield | April 23 | May 6 | October 17 | October 1 | 176 days | 5b |
| Davenport | April 23 | May 8 | October 15 | October 1 | 174 days | 5a |
| Glenwood3 mi SW | April 23 | May 6 | October 11 | September 27 | 170 days | – |
| Oakland | April 23 | May 5 | October 14 | September 30 | 174 days | 5b |
| OttumwaOttumwa Industrial Airport | April 23 | May 7 | October 14 | September 29 | 172 days | 5b |
| Albia3 mi NNE | April 24 | May 9 | October 16 | September 29 | 173 days | 5b |
| Bedford | April 24 | May 6 | October 15 | October 1 | 173 days | – |
| Colo | April 24 | May 7 | October 12 | September 28 | 170 days | 5b |
| Indianola2 mi W | April 24 | May 8 | October 12 | September 27 | 168 days | 5b |
| Muscatine | April 24 | May 9 | October 14 | October 1 | 172 days | 5b |
| Red Oak | April 24 | May 8 | October 13 | September 26 | 169 days | 5b |
| Sigourney | April 24 | May 9 | October 15 | September 30 | 172 days | 5b |
| BellevueBellevue Lock and Dam 12 | April 25 | May 11 | October 16 | October 1 | 172 days | 5a |
| CastanaCastana Experiment Farm | April 25 | May 7 | October 12 | September 28 | 170 days | 5b |
| Clarinda | April 25 | May 7 | October 11 | September 26 | 168 days | 5b |
| Greenfield | April 25 | May 7 | October 12 | September 26 | 170 days | 5b |
| Maquoketa | April 25 | May 9 | October 14 | September 30 | 171 days | 5a |
| Mount Ayr | April 25 | May 9 | October 12 | September 27 | 169 days | 5a |
| Perry | April 25 | May 8 | October 10 | September 25 | 166 days | 5a |
| Storm Lake | April 25 | May 7 | October 13 | October 1 | 170 days | 5b |
| AmesAmes Municipal Airport | April 26 | May 9 | October 8 | September 23 | 164 days | 5a |
| Ames (5 mi SE) | April 26 | May 8 | October 12 | September 26 | 168 days | 5a |
| Columbus Junction | April 26 | May 11 | October 10 | September 23 | 167 days | – |
| Dakota City | April 26 | May 7 | October 12 | September 29 | 169 days | – |
| Jefferson | April 26 | May 8 | October 9 | September 23 | 164 days | 5b |
| Keosauqua | April 26 | May 11 | October 13 | September 28 | 169 days | 5b |
| Pocahontas | April 26 | May 8 | October 7 | September 25 | 164 days | 5a |
| Rockwell City | April 26 | May 6 | October 10 | September 27 | 167 days | 5a |
| Allison | April 27 | May 8 | October 8 | September 24 | 165 days | 5a |
| Anamosa (3 mi SSW) | April 27 | May 10 | October 13 | September 30 | 170 days | – |
| Carroll | April 27 | May 8 | October 10 | September 25 | 166 days | 5b |
| Cedar RapidsCedar Rapids Municipal Airport | April 27 | May 11 | October 11 | September 25 | 165 days | 5a |
| Corning | April 27 | May 11 | October 12 | September 26 | 168 days | 5b |
| Denison | April 27 | May 9 | October 11 | September 27 | 166 days | 5b |
| Eldora | April 27 | May 8 | October 10 | September 27 | 165 days | 5a |
| Emmetsburg | April 27 | May 9 | October 7 | September 23 | 164 days | 5a |
| Fairfield | April 27 | May 14 | October 12 | September 27 | 168 days | 5b |
| Harlan | April 27 | May 9 | October 9 | September 24 | 165 days | 5b |
| HumboldtHumboldt Water Treatment Plant | April 27 | May 7 | October 9 | September 24 | 166 days | – |
| Ida Grove5 mi NW | April 27 | May 11 | October 12 | September 27 | 167 days | – |
| Lowden | April 27 | May 13 | October 10 | September 25 | 165 days | 5a |
| Oelwein (1 mi E) | April 27 | May 10 | October 13 | September 30 | 169 days | 4b |
| WaterlooWaterloo Municipal Airport | April 27 | May 10 | October 10 | September 26 | 165 days | 5a |
| Belle Plaine | April 28 | May 11 | October 10 | September 26 | 165 days | 5a |
| Boone | April 28 | May 11 | October 12 | September 28 | 165 days | 5a |
| Cascade | April 28 | May 12 | October 10 | September 28 | 164 days | 5a |
| Centerville | April 28 | May 11 | October 14 | September 26 | 168 days | – |
| Creston2 mi SW | April 28 | May 9 | October 11 | September 24 | 164 days | – |
| DubuqueDubuque Regional Airport | April 28 | May 12 | October 11 | September 28 | 165 days | 5a |
| Fort Dodge5 mi NNW | April 28 | May 9 | October 8 | September 24 | 162 days | 5a |
| Iowa Falls | April 28 | May 11 | October 10 | September 26 | 164 days | 5a |
| MarionCedar Rapids #1 | April 28 | May 13 | October 12 | September 29 | 166 days | 5b |
| Marshalltown station | April 28 | May 11 | October 7 | September 22 | 162 days | 5a |
| Spirit Lake | April 28 | May 9 | October 11 | September 27 | 164 days | 5a |
| Washington | April 28 | May 11 | October 11 | September 25 | 165 days | 5b |
| Williamsburg1 mi E | April 28 | May 12 | October 9 | September 24 | 164 days | 5a |
| Britt3 mi E | April 29 | May 10 | October 7 | September 24 | 161 days | 5a |
| Grundy Center | April 29 | May 12 | October 9 | September 25 | 160 days | 5a |
| Hampton | April 29 | May 10 | October 9 | September 26 | 162 days | 5a |
| Iowa City station | April 29 | May 14 | October 9 | September 25 | 162 days | 5b |
| Logan | April 29 | May 13 | October 8 | September 23 | 162 days | 5a |
| Mason City station | April 29 | May 9 | October 7 | September 25 | 161 days | 5a |
| Osceola | April 29 | May 11 | October 9 | September 24 | 162 days | 5a |
| Primghar | April 29 | May 11 | October 10 | September 26 | 163 days | 5a |
| Sioux CitySioux City Airport | April 29 | May 14 | October 5 | September 22 | 159 days | 5a |
| Sioux City Ang | April 29 | May 11 | October 7 | September 24 | 161 days | 5b |
| Tripoli | April 29 | May 9 | October 9 | September 25 | 162 days | 5a |
| Algona | April 30 | May 11 | October 6 | September 23 | 160 days | 5a |
| Atlantic1 mi NE | April 30 | May 15 | October 2 | September 17 | 153 days | 5a |
| Charles City | April 30 | May 14 | October 6 | September 21 | 157 days | 4b |
| Clarion | April 30 | May 12 | October 10 | September 27 | 162 days | – |
| Forest City2 mi NNE | April 30 | May 10 | October 7 | September 22 | 159 days | – |
| Holstein | April 30 | May 11 | October 9 | September 27 | 162 days | – |
| IndependenceIndependence #1 | April 30 | May 12 | October 7 | September 23 | 159 days | – |
| Lake Park | April 30 | May 11 | October 10 | September 26 | 164 days | 5a |
| Le Mars | April 30 | May 12 | October 4 | September 21 | 157 days | 5a |
| Leon6 mi ESE | April 30 | May 15 | October 8 | September 26 | 161 days | 5a |
| MarshalltownMarshalltown Municipal Airport | April 30 | May 12 | October 6 | September 22 | 159 days | 5a |
| Mount Pleasant1 mi SSW | April 30 | May 14 | October 10 | September 24 | 163 days | 5b |
| Oelwein2 mi S | April 30 | May 13 | October 9 | September 26 | 163 days | – |
| Osage | April 30 | May 12 | October 9 | September 25 | 163 days | 5a |
| Sac City | April 30 | May 11 | October 6 | September 23 | 158 days | 5a |
| Sioux Center2 mi SE | April 30 | May 12 | October 3 | September 19 | 154 days | 5a |
| Sioux Rapids4 mi E | April 30 | May 11 | October 5 | September 22 | 159 days | 5a |
| Toledo3 mi N | April 30 | May 11 | October 9 | September 26 | 162 days | 5a |
| Winterset1 mi S | April 30 | May 11 | October 3 | September 20 | 157 days | 5a |
| Anamosa1 mi WNW | May 1 | May 18 | October 4 | September 21 | 154 days | 5a |
| Battle Creek3 mi NE | May 1 | May 15 | October 1 | September 18 | 153 days | – |
| Hawarden | May 1 | May 14 | October 4 | September 21 | 155 days | 5a |
| Little Sioux2 mi NW | May 1 | May 12 | October 3 | September 20 | 155 days | 5a |
| Milford4 mi NW | May 1 | May 14 | October 6 | September 24 | 158 days | 5a |
| Onawa3 mi NW | May 1 | May 13 | October 3 | September 21 | 154 days | 5a |
| Postville | May 1 | May 14 | October 3 | September 20 | 153 days | – |
| Rock Rapids | May 1 | May 13 | October 4 | September 21 | 156 days | 5a |
| Sanborn | May 1 | May 13 | October 7 | September 23 | 160 days | 5a |
| Spencer (1 mi N) | May 1 | May 14 | October 3 | September 20 | 154 days | 4b |
| Audubon | May 2 | May 15 | October 3 | September 19 | 154 days | 5a |
| EsthervilleEstherville Municipal Airport | May 2 | May 14 | September 30 | September 17 | 150 days | 5a |
| Estherville (4 mi E) | May 2 | May 14 | October 3 | September 20 | 153 days | 5a |
| Guthrie Center | May 2 | May 17 | October 3 | September 20 | 153 days | 5a |
| New Hampton | May 2 | May 14 | October 5 | September 23 | 155 days | 5a |
| SpencerSpencer Municipal Airport | May 2 | May 15 | October 2 | September 18 | 154 days | 4b |
| Waukon | May 2 | May 16 | October 11 | September 28 | 161 days | – |
| Coggon | May 3 | May 17 | October 7 | September 22 | 156 days | – |
| Decorah | May 3 | May 16 | October 7 | September 25 | 157 days | 4b |
| Grinnell3 mi SW | May 3 | May 17 | October 6 | September 22 | 155 days | 5a |
| ManchesterManchester #2 | May 3 | May 16 | October 4 | September 22 | 154 days | 5a |
| MapletonMapleton No.2 | May 3 | May 16 | October 1 | September 19 | 151 days | 5a |
| Mason CityMason City Municipal Airport | May 3 | May 15 | October 1 | September 18 | 150 days | 5a |
| Vinton | May 3 | May 17 | October 3 | September 20 | 151 days | 5a |
| Webster City | May 3 | May 16 | October 2 | September 18 | 150 days | 5a |
| Cherokee | May 4 | May 17 | October 4 | September 20 | 152 days | 4b |
| Fayette | May 4 | May 17 | October 4 | September 20 | 151 days | 4b |
| Northwood | May 4 | May 16 | October 4 | September 20 | 152 days | 4b |
| Stanley | May 4 | May 15 | October 1 | September 16 | 150 days | – |
| Swea City5 mi N | May 4 | May 14 | October 1 | September 18 | 150 days | – |
| Chariton1 mi E | May 5 | May 19 | October 5 | September 20 | 151 days | 5a |
| Sheldon | May 5 | May 18 | September 28 | September 14 | 145 days | 4b |
| Sibley | May 5 | May 17 | October 3 | September 21 | 152 days | 4b |
| Cresco1 mi NE | May 8 | May 21 | October 1 | September 19 | 147 days | 4b |
| Elkader6 mi SSW | May 8 | May 22 | October 1 | September 18 | 146 days | 4a |
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities, growing-season length); station daily lows via ACIS (zone). Growing season: NOAA's median number of days between the last spring and first autumn 32°F night. Zone: the USDA's plant hardiness rule applied to the station's own 1991-2020 coldest nights.