Zones across Iowa
Share of Iowa's 1,042 ZIP codes in each zone:
Frost dates in Iowa
Median 32°F freeze dates across 1,042 ZIP codes with a NOAA weather station within 60 km, from the 1991 to 2020 climate normals. Frost dates vary a lot inside a state, so look up your ZIP code for your own dates.
Sources: NOAA NCEI U.S. Climate Normals 1991 to 2020; Purdue Extension, Indiana Vegetable Planting Calendar (HO-186-W).
Places in each zone
| Zone | Average coldest night | Example places |
|---|---|---|
| 4b | -25 to -20°F (-32 to -29°C) | Riceville, Arlington, Elma, Sibley, Delaware, Edgewood |
| 5a | -20 to -15°F (-29 to -26°C) | Sioux City, Cedar Rapids, Dubuque, Waterloo, Boone, Mason City |
| 5b | -15 to -10°F (-26 to -23°C) | Des Moines, Davenport, Iowa City, Cedar Rapids, Ames, Clinton |
| 6a | -10 to -5°F (-23 to -21°C) | Council Bluffs, Carter Lake, Glenwood, Silver City, Tabor, Cantril |
Zones for cities in Iowa
Using your zone in Iowa
Zones measure winter cold only: the average of the coldest night each year from 1991 to 2020. Within Iowa, zones change with elevation, latitude and distance from large bodies of water, so two towns a short drive apart can differ by a half zone or more. Check your own ZIP code, then pick perennials, shrubs and trees whose tag range includes your zone.
What changed on the 2023 map
The 2023 map, released by the USDA and Oregon State University's PRISM Climate Group, uses weather data from 1991 to 2020 and far more weather stations than the 2012 map. Nationally, about half the country moved to the next warmer half zone and the rest stayed in the same half zone, so if your plant tags or old garden notes use a 2012 zone for Iowa, it is worth checking your ZIP code again.
Frequently asked questions
What planting zone is Iowa?
Iowa spans USDA plant hardiness zones 4b to 6a on the 2023 map. The most common zone by ZIP code is 5a.
How do I find my exact zone in Iowa?
Zones can change over short distances with elevation and nearness to water. Enter your ZIP code in the zone finder for the zone the 2023 USDA map gives your ZIP code.
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code listings, PRISM Climate Group, Oregon State University. Place names: GeoNames (CC BY 4.0). Not the official USDA map.