Iowa Planting Zones by City and ZIP Code
Iowa runs from zones 4b to 6a; 54% of its ZIPs are 5a, Des Moines is 5b and Cedar Rapids is 5b.
Iowa runs from zones 4b to 6a
The coldest night of the winter averages -25°F to -20°F in the coldest of Iowa’s ZIP codes and -10°F to -5°F in the warmest. Most of the state is zone 5a.
Planting zones of Iowa cities
| City | Zone | Coldest night, on average | Since 2012 |
|---|---|---|---|
| Des Moines50309 | 5b | -15°F to -10°F | same as 2012 |
| Cedar Rapids52401 | 5b | -15°F to -10°F | half a zone warmer than 2012 (5a) |
| Davenport52801 | 5b | -15°F to -10°F | same as 2012 |
| Sioux City51101 | 5a | -20°F to -15°F | same as 2012 |
| Dubuque52001 | 5a | -20°F to -15°F | same as 2012 |
| Mason City50401 | 5a | -20°F to -15°F | same as 2012 |
Tap a ZIP for that address’s frost dates and this month’s jobs.
Find your zone anywhere in Iowa
A ZIP code or a town gives you its zone, how it moved since 2012, the frost dates at the nearest NOAA station, and the jobs for this month timed from them.
What to plant in Iowa this month
The calendar for each of Iowa's main zones, from vegetables to pruning and winter protection, each job tied to the extension page it comes from. Pick a month, or read the whole year below it.
Timed from the median frost dates of the 84 NOAA stations in Iowa’s zone 5a: last spring frost Apr 30, first fall frost Oct 7. Your own ZIP’s frost dates move every window, so the ZIP tool times them for you.
Pick a month above to see every job in it.
The year at a glance
- Start vegetable seeds indoorsJan to Apr
- Sow vegetables in the gardenApr to May
- Sow the fall vegetable gardenJun to Aug
- Set out transplantsApr to May
- Plant trees and shrubsMar 19 to May 14 and Sep 23 to Nov 11
- Plant garlicSep 23 to Oct 28
- Plant tulips and other spring bulbsOct 14 to Oct 21
- Divide fall-blooming perennialsApr 9 to May 21
- Divide spring and summer-blooming perennialsAug 26 to Oct 7
- Prune trees and summer-flowering shrubs while dormantFeb 19 to Apr 2
- Prune spring-flowering shrubs after they bloomApr 16 to Jun 11
- Water evergreens and new plantings until the ground freezesSep 9 to Nov 18
- Mulch perennial crowns once the ground freezesNov 18 to Dec 2
- Pull back the winter mulchMar 12 to Mar 26
- Put hardware cloth around young tree trunksOct 7 to Nov 18
- Dig and store canna, dahlia and gladiolusOct 7 to Oct 14
- Cut back perennials after a hard freezeOct 14 to Nov 11
What changed in Iowa since 2012
Every ZIP on both mapsCompared ZIP by ZIP from the 2023 and 2012 USDA tables; 1,042 Iowa ZIP codes appear in both.
Why Iowa’s zones moved
Of the cities above, Cedar Rapids went from 5a to 5b.
The USDA explains the national picture: “When compared to the 2012 map, the 2023 version reveals that about half of the country shifted to the next warmer half zone, and the other half of the country remained in the same half zone.” The new map uses 1991 to 2020 and more than 13,000 weather stations, so it draws Iowa’s hills, valleys and cities more finely than the 2012 map did.
A warmer zone changes which perennials and shrubs come through the winter, not when the garden gets planted; that still follows the frost dates.
Frost dates and seed starting in Iowa
Iowa planting zone questions
Planting zones by state
Sources. USDA Plant Hardiness Zone Map, ZIP code tables (2023 and 2012), PRISM Climate Group, Oregon State University; USDA Plant Hardiness Zone Map; USDA Unveils Updated Plant Hardiness Zone Map (USDA Agricultural Research Service, November 15, 2023); NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal, by station (v1.0.1); NC State Extension Gardener Plant Toolbox. Zones are read from the PRISM ZIP code tables, read Oct 9, 2026; a ZIP code’s zone is the zone at its center. The calendar’s extension sources are listed on the planting zones page and under each job.