In Iowa, the last spring frost usually comes between April 25 and May 8, and the first fall frost between September 28 and October 13, depending on where you live. Most of Iowa is in USDA hardiness zones 5a to 5b.
Find the frost dates for your ZIP code
Frost dates from NOAA 1991–2020 U.S. Climate Normals, nearest weather station. Zones derived from the 2023 USDA Plant Hardiness Zone Map data (PRISM Climate Group, Oregon State University). This is not the official USDA Plant Hardiness Zone Map.
Frost dates for Iowa cities
Dates come from the NOAA weather station closest to each city. The last spring frost and first fall frost are the typical dates, with a 30% chance of frost after (or before) them. The safer planting date has only a 10% chance of a later spring frost: use it for tender plants like tomatoes, peppers and basil.
| City | Zone | Last frost | Safer date | First frost |
|---|---|---|---|---|
| Des Moines | 5b | April 24 | May 2 | Oct. 14 |
| Cedar Rapids | 5b | May 4 | May 13 | Oct. 7 |
| Davenport | 5b | April 24 | May 4 | Oct. 17 |
| Sioux City | 5a | May 4 | May 11 | Oct. 1 |
| Waterloo | 5a | May 2 | May 10 | Oct. 4 |
| Ames | 5b | May 2 | May 9 | Oct. 2 |
| Council Bluffs | 5b | April 23 | April 30 | Oct. 15 |
| Dubuque | 5a | April 25 | May 4 | Oct. 16 |
| Marshalltown | 5a | May 3 | May 11 | Oct. 1 |
| Mason City | 5a | May 3 | May 9 | Oct. 1 |
Frost dates vary a lot across Iowa. Among the cities above, Council Bluffs has the earliest last frost (around April 23) and Cedar Rapids the latest (around May 4), about 2 weeks apart. Elevation, nearby water and local terrain all make a difference, so use the dates for the place closest to you, or look up your ZIP code.
Growing zones in Iowa
Most of Iowa is in USDA hardiness zones 5a to 5b. A typical frost-free growing season lasts about 173 days, longer in the warmest areas and shorter in the coldest.
Find planting dates for the main zones in Iowa:
- Zone 5 (about 95% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
See all crops in our planting guides, or build a planting calendar for your ZIP code.
How to use frost dates
- Cool-season crops such as peas, lettuce, spinach and onions can go in several weeks before your last spring frost.
- Warm-season crops such as tomatoes, peppers, squash and beans wait until after it, when the soil has warmed.
- Fall crops are timed back from your first fall frost, and garlic and tulips are planted around it.
- Frost dates are averages. Check the forecast before setting out tender plants.
Frequently asked questions
When is the last frost in Iowa?
It depends on where you live. Across most of Iowa, the last spring frost comes between April 25 and May 8. In Des Moines, it is around April 24.
When is the first frost in Iowa?
Across most of Iowa, the first fall frost comes between September 28 and October 13. In Des Moines, it is around October 14.
What planting zone is Iowa?
Most of Iowa is in USDA hardiness zones 5a to 5b. Enter your ZIP code above to find your exact zone.
When can I plant tomatoes in Iowa?
Plant tomatoes outside after your last frost, once nights stay above 50 °F. In Des Moines, the safer date, with only a 10% chance of a later frost, is around May 2. See when to plant tomatoes in zone 5.
Sources. Frost dates come from the nearest NOAA weather station to each city or ZIP code. Zones come from the 2023 USDA Plant Hardiness Zone Map ZIP code data. Our zone lookup is not the official USDA map.