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Frost Dates and Planting Windows in Iowa

The 32°F frost dates at the 150 weather stations in Iowa with NOAA's 1991–2020 Climate Normals, and the planting windows they give. These are long-term statistics, not a forecast. For the dates at the station nearest you, enter your ZIP code.

The planner uses the weather station nearest your ZIP code.

Frost dates across Iowa

Each risk level uses a date with a set chance of frost. In spring, it's the chance of a 32°F frost on or after the last-frost date. In fall, it's the chance of the first 32°F frost on or before the first-frost date. At the Typical level (30%), the last frost ranges from April 17 to May 14 across the state, and the first frost from September 23 to October 21.

32°F frost dates: earliest and latest among 150 stations, by risk level
Risk levelEarliest last frostLatest last frostEarliest first frostLatest first frost
Conservative (10%)April 262 stationsMay 22ELKADER 6 SSW, IA USSeptember 14SHELDON, IA USOctober 112 stations
Typical (30%)April 17KEOKUK LOCK DAM 19, IA USMay 142 stationsSeptember 23SHELDON, IA USOctober 21KEOKUK LOCK DAM 19, IA US
Aggressive (50%)April 10KEOKUK LOCK DAM 19, IA USMay 82 stationsSeptember 28SHELDON, IA USOctober 27KEOKUK LOCK DAM 19, IA US

Growing season length

The growing season is the stretch between the last spring frost and the first fall frost at 32°F. NOAA gives it as a length with a chance of being at least that long. Each risk level uses the length with that chance of a shorter season, so Conservative shows the shortest lengths.

Growing season at 32°F: shortest and longest among 150 stations
Risk levelShortestLongest
Conservative (90% chance of at least this long)126 daysELKADER 6 SSW, IA US177 daysKEOKUK LOCK DAM 19, IA US
Typical (70% chance of at least this long)138 days3 stations190 daysKEOKUK LOCK DAM 19, IA US
Aggressive (50% chance of at least this long)145 daysSHELDON, IA US198 daysKEOKUK LOCK DAM 19, IA US
Number of stations by growing season length, Typical (70% chance of at least this long)
Growing seasonStations
120–139 days3
140–159 days93
160–179 days50
180–199 days4

Planting windows across Iowa

For each crop, the earliest start and the latest end of its Typical windows among the stations. A window at any one station is shorter and falls inside this span. Transplant dates are for seedlings.

Typical planting windows (30% frost dates): earliest start and latest end among stations
Crop and taskEarliest startLatest endStations
Basil: Transplant outdoorsMay 1May 28150 of 150
Bean: Sow outdoorsApril 17May 14150 of 150
Beet: Sow outdoorsMarch 20May 14150 of 150
Beet: Sow for fallJuly 1September 1150 of 150
Broccoli: Transplant outdoorsMarch 20April 30150 of 150
Broccoli: Transplant for fallJune 21September 1150 of 150
Brussels sprouts: Transplant outdoorsMarch 20April 30150 of 150
Brussels sprouts: Transplant for fallJune 1September 11150 of 150
Cabbage: Transplant outdoorsMarch 20April 30150 of 150
Cabbage: Transplant for fallJune 16September 1150 of 150
Cantaloupe: Transplant outdoorsMay 1May 28150 of 150
Cantaloupe: Sow outdoorsMay 1May 28150 of 150
Carrot: Sow outdoorsMarch 20May 14150 of 150
Carrot: Sow for fallJune 21August 22150 of 150
Cucumber: Transplant outdoorsApril 24May 21150 of 150
Cucumber: Sow outdoorsApril 17May 14150 of 150
Eggplant: Transplant outdoorsMay 1May 28150 of 150
Garlic: Plant for fallSeptember 23November 4150 of 150
Lettuce: Transplant outdoorsMarch 20April 30150 of 150
Lettuce: Sow outdoorsMarch 20April 30150 of 150
Lettuce: Sow for fallJune 21September 11150 of 150
Onion: Transplant or plant setsMarch 20April 30150 of 150
Peas: Sow outdoorsMarch 20April 30150 of 150
Peas: Sow for fallJune 29September 1150 of 150
Pepper: Transplant outdoorsMay 1May 28150 of 150
Potato: Plant seed potatoesMarch 20May 14150 of 150
Pumpkin: Sow outdoorsMay 1May 28150 of 150
Radish: Sow outdoorsMarch 20April 30150 of 150
Radish: Sow for fallAugust 5October 1150 of 150
Spinach: Transplant outdoorsMarch 20April 30150 of 150
Spinach: Sow outdoorsMarch 20April 30150 of 150
Spinach: Sow for fallJuly 11September 14150 of 150
Summer squash: Transplant outdoorsApril 24May 21150 of 150
Summer squash: Sow outdoorsApril 17May 14150 of 150
Sweet corn: Sow outdoorsApril 17May 14150 of 150
Sweet potato: Plant slipsApril 24May 28150 of 150
Tomato: Transplant outdoorsMay 1May 28150 of 150
Turnip: Sow outdoorsMarch 20April 30150 of 150
Turnip: Sow for fallJuly 11September 11150 of 150
Watermelon: Transplant outdoorsMay 1May 28150 of 150
Watermelon: Sow outdoorsMay 1May 28150 of 150

Weather stations in Iowa

Every station in Iowa with NOAA frost-date normals, with its Typical 32°F frost dates and growing season.

Data sources

NOAA U.S. Climate Normals, frost dates, 1991–2020 normals, version 1.0.1
Files: us-climate-normals_1991-2020_v1.0.1_annualseasonal_multivariate_by-station_c20230404.tar.gz, inventory_30yr.txt from NOAA NCEI. Retrieved October 10, 2026.