Frost dates / By state
Frost dates in Iowa
NOAA 1991–2020 normals for a 32 °F freeze. Your own yard can run a little either side.
Short answer
Across 17 NOAA weather stations in Iowa, the average last spring frost runs from April 15 at Burlington Muni Airport to May 3 at Mason City Muni Airport. The first fall frost comes as early as September 30 at Estherville Muni Airport and as late as October 21 at Lamoni Muni Airport. Planting zones near these stations run from 5a to 6a.
Iowa cities
- Frost dates in Des Moines: last frost April 18, first frost October 20
Find yours by ZIP code
The table below is by weather station. For the station nearest you, and your planting zone, type your ZIP code.
Iowa frost dates by weather station
| Station | Last spring frost | First fall frost | Frost-free | Zone nearby |
|---|---|---|---|---|
| Ames Muni Airport 930 ft | April 26 1 in 10 after May 9 | October 8 1 in 10 by September 23 | 165 days | 5b |
| Burlington Muni Airport 692 ft | April 15 1 in 10 after May 1 | October 20 1 in 10 by October 6 | 188 days | 6a |
| Cedar Rapids Muni Airport 868 ft | April 27 1 in 10 after May 11 | October 11 1 in 10 by September 25 | 167 days | 5a |
| Davenport 754 ft | April 23 1 in 10 after May 8 | October 15 1 in 10 by October 1 | 175 days | 5b |
| Des Moines 17 E 921 ft | April 21 1 in 10 after May 5 | October 15 1 in 10 by September 30 | 177 days | 5b |
| Des Moines Intl Airport 957 ft | April 18 1 in 10 after May 2 | October 20 1 in 10 by October 4 | 185 days | 5b |
| Dubuque Rgnl Airport 1,056 ft | April 28 1 in 10 after May 12 | October 11 1 in 10 by September 28 | 166 days | 5a |
| Estherville Muni Airport 1,317 ft | May 2 1 in 10 after May 14 | September 30 1 in 10 by September 17 | 151 days | 5a |
| Iowa City Muni Airport 650 ft | April 21 1 in 10 after May 6 | October 18 1 in 10 by October 4 | 180 days | 5b |
| Lamoni 1,168 ft | April 16 1 in 10 after May 2 | October 20 1 in 10 by October 6 | 187 days | 5b |
| Lamoni Muni Airport 1,131 ft | April 16 1 in 10 after May 2 | October 21 1 in 10 by October 6 | 188 days | 5b |
| Marshalltown Muni Airport 974 ft | April 30 1 in 10 after May 12 | October 6 1 in 10 by September 22 | 159 days | 5a |
| Mason City Muni Airport 1,225 ft | May 3 1 in 10 after May 15 | October 1 1 in 10 by September 18 | 151 days | 5a |
| Ottumwa Industrial Airport 842 ft | April 23 1 in 10 after May 7 | October 14 1 in 10 by September 29 | 174 days | 5b |
| Sioux City Gateway Airport 1,095 ft | April 29 1 in 10 after May 14 | October 5 1 in 10 by September 22 | 159 days | 5a |
| Spencer Muni Airport 1,338 ft | May 2 1 in 10 after May 15 | October 2 1 in 10 by September 18 | 153 days | 5a |
| Waterloo Muni Airport 868 ft | April 27 1 in 10 after May 10 | October 10 1 in 10 by September 26 | 166 days | 5a |
The average date is NOAA's 50% date: half of years have a later last frost, or an earlier first one. Plan by the 1-in-10 date if a freeze would cost you plants. Stations are NOAA's main weather stations, mostly airports. “Zone nearby” is the USDA 2023 zone of the nearest ZIP code within 10 miles. NOAA counts the frost season from August to July, so in the warmest places the “first fall” freeze lands after New Year.
How these dates work
Frost dates come from NOAA's 1991 to 2020 Climate Normals, which work out from each weather station's daily lows how likely the last spring freeze and the first fall freeze (32 °F) are by each date. We use the station nearest the middle of your ZIP code and show its height and distance, since a station on a hill or by a lake can differ from your yard.
The average date is the 50% date: half of years have a freeze after the spring date or before the fall one. The 1-in-10 dates are NOAA's 10% dates, the ones to plan by if a late freeze would cost you plants. Within one yard, cold air pools in low spots while walls and paving hold heat, so some corners freeze before others.
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Where the numbers come from
- USDA Plant Hardiness Zone Map, 2023. Agricultural Research Service, U.S. Department of Agriculture
- PRISM Climate Group, Oregon State University (zone data)
- NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal
- NOAA, Normals calculation methodology (frost-freeze probability dates)
- US Census Bureau, 2025 ZCTA gazetteer (ZIP code centers)