This page has no affiliate links and no product recommendations — it points you to the right state calendar.
No single planting calendar can cover the Midwest. The four states on this page stretch from 129 frost-free days in Dickinson, North Dakota, to 187 in Burlington, Iowa — a 58-day spread. A schedule written for one end of it would be wrong for the other in nearly every month. That is why this page does not publish one regional schedule. Instead, it compares the four state calendars below, each built the same way — from its own state’s Extension schedule and its own NOAA frost anchors — and points you to the one written for your state.
Illinois Extension’s own planting page splits a single state into northern, central, and southern regions. If one state needs three sets of dates, a twelve-state region is not going to fit in one table. The four states on this page alone run from Zone 3 in northern Minnesota to Zone 6a in southern Iowa, and the wider Midwest runs warmer still to the south.
How to use this page: find your state in the frost table, then open its calendar. If your state is not covered yet, the section near the bottom says what comes next.
Compare frost seasons across the four states
All dates below are NOAA NCEI 1991–2020 U.S. Climate Normals, 50%-probability, 32°F freeze tables — the same basis used on each state page. The 50% figure is a coin flip, not a guarantee: the last spring frost date is the date after which there is about a 50% chance of no more 32°F freezes, and the first fall frost date is the date before which there is about a 50% chance of the first 32°F freeze. In any given year, frost can come earlier or later.
| Station | State | Last spring frost (50%) | First fall frost (50%) | Frost-free season | Elevation |
|---|---|---|---|---|---|
| Duluth (USW00014913) | Minnesota | May 13 | October 1 | 140 days | 1,428 ft |
| St. Cloud (USW00014926) | Minnesota | May 7 | September 30 | 144 days | 1,018 ft |
| Minneapolis–St. Paul (USW00014922) | Minnesota | April 23 | October 18 | 176 days | 872 ft |
| Mason City (USW00014940) | Iowa | May 3 | October 1 | 150 days | 1,225 ft |
| Cedar Rapids (USW00014990) | Iowa | April 27 | October 11 | 165 days | 868 ft |
| Sioux City (USW00014943) | Iowa | April 29 | October 5 | 159 days | 1,095 ft |
| Des Moines (USW00014933) | Iowa | April 18 | October 20 | 184 days | 957 ft |
| Burlington (USW00014931) | Iowa | April 15 | October 20 | 187 days | 692 ft |
| Aberdeen (USW00014929) | South Dakota | May 9 | September 26 | 139 days | 1,302 ft |
| Rapid City (USW00024090) | South Dakota | May 12 | October 1 | 139 days | 3,160 ft |
| Sioux Falls (USW00014944) | South Dakota | May 1 | October 6 | 157 days | 1,430 ft |
| Minot (USW00024013) | North Dakota | May 10 | October 1 | 144 days | 1,665 ft |
| Devils Lake (USW00014912) | North Dakota | May 6 | October 5 | 152 days | 1,464 ft |
| Fargo (USW00014914) | North Dakota | May 10 | September 30 | 143 days | 900 ft |
| Bismarck (USW00024011) | North Dakota | May 14 | September 27 | 136 days | 1,658 ft |
| Dickinson (USW00024012) | North Dakota | May 18 | September 25 | 129 days | 2,580 ft |
The spread is the point. Dickinson, North Dakota, averages 129 frost-free days; Burlington, Iowa, averages 187. That is 58 days — nearly two months — between two stations in the same four-state region. A single schedule written for both would be wrong for one of them in almost every month. Each state below has its own calendar because each state’s Extension service publishes its own schedule, and each schedule is anchored to its own frost dates.
Pick your state
Minnesota. Three frost bands — north (Zones 3–4), central (Zone 4), and south (Zones 4b–5) — with 25 crops and planting windows from University of Minnesota Extension, anchored to the Duluth, St. Cloud, and Minneapolis–St. Paul stations above. Start with the Minnesota planting calendar.
Iowa. One statewide chart — Iowa State Extension’s HORT 3124 — with dates for central Iowa and a shift of about one week earlier in the south and one week later in the north, 43 crops, and a second season in July. Start with the Iowa planting calendar.
South Dakota. One statewide table from SDSU Extension’s booklet, localized the way the booklet itself directs: pair the schedule with frost maps, here the South Dakota Mesonet’s percentile frost maps, to read your own dates off your own location. Start with the South Dakota planting calendar.
North Dakota. No statewide schedule exists — NDSU Extension says the calendar approach may not work for direct sowing — so this calendar follows the soil-temperature method instead, with frost dates as guardrails. Start with the North Dakota planting calendar.
States not covered yet
Wisconsin, Illinois, Michigan, Ohio, Indiana, Missouri, Kansas, and Nebraska are not covered yet. This page covers the four states above for now, and new states will be added here as their calendars are published.
Sources
Frost dates: NOAA NCEI 1991–2020 U.S. Climate Normals, 50%-probability, 32°F freeze tables, as published on each state page. Planting schedules: University of Minnesota Extension (Minnesota), Iowa State Extension HORT 3124 (Iowa), SDSU Extension’s Vegetable Gardening in South Dakota booklet (South Dakota), and NDSU Extension columns (North Dakota). Each calendar’s full source trace — every Extension window, station table, and variety figure behind it — is on its own page: the Minnesota planting calendar, the Iowa planting calendar, the South Dakota planting calendar, and the North Dakota planting calendar.
