USDA zone 4a in Minnesota
USDA plant hardiness zone 4a covers 49 locations across Minnesota (average annual extreme minimum −30 to −25 °F): Aitkin, MN, Argyle, MN, Askov, MN, Baxter, MN, Beaulieu, MN, Bejou, MN, and 43 more. Average last spring frost across this group ranges May 1 (Nashua) to June 5 (Hibbing), and growing seasons run 93–160 days (Hibbing to Nashua) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Minnesota location's own frost dates; the printable planting calendar uses Pine, this group's median-season location.
- USDA zone
- 4a−30 to −25 °F
- Last frost range
- May 1–Jun 5avg, 32°F
- First frost range
- Sep 8–Oct 9avg, 32°F
- Growing season range
- 93–160days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Aitkin | — | Aitkin 2e | May 16 | Sep 28 | 133 |
| Argyle | Warren, Stephen, Oslo, Donaldson, Alvarado | Argyle | May 15 | Sep 26 | 134 |
| Askov | Kerrick | Bruno 7ene | May 18 | Sep 26 | 129 |
| Baxter | Brainerd, Fort Ripley | Brainerd | May 8 | Sep 29 | 141 |
| Beaulieu | Twin Lakes | Mahnomen | May 7 | Sep 28 | 143 |
| Bejou | — | Fosston 1 E | May 15 | Sep 26 | 132 |
| Brookston | Meadowlands | Duluth | May 13 | Oct 1 | 140 |
| Cloquet | Carlton, Big Lake, Brookston | Cloquet | May 26 | Sep 23 | 118 |
| Crookston | Climax, Fisher | Crookston Nw Exp Stn | May 11 | Sep 27 | 138 |
| Deerwood | Riverton | Brainerd Crow Wing Co Ap | May 13 | Sep 27 | 138 |
| Detroit Lakes | White Earth, Vergas, Frazee, Lake Park, Audubon, Callaway | Detroit Lakes 1 Nne | May 15 | Sep 24 | 130 |
| Emily | Fifty Lakes, Crosslake, Trommald, Pine River, Hill | Pine Rvr Dam | May 6 | Oct 7 | 152 |
| Fergus Falls | — | Fergus Falls | May 4 | Oct 5 | 152 |
| Fertile | Beltrami, Ada, Ulen, Hitterdal, Twin Valley, Gary, +4 more | Ada | May 11 | Sep 27 | 137 |
| Finlayson | — | Sandstone 6 W | May 13 | Sep 29 | 137 |
| Grand Marais | — | Grand Portage | May 24 | Sep 29 | 127 |
| Hackensack | Backus | Deep Portage | May 5 | Oct 5 | 150 |
| Hibbing | Calumet | Hibbing Chisholm Hibbing Ap | Jun 5 | Sep 8 | 93 |
| Isle | Garrison, Onamia, Wahkon, McGrath | Isle 12n | May 10 | Oct 3 | 144 |
| Kennedy | — | Hallock | May 8 | Sep 30 | 142 |
| Little Falls | Flensburg, Royalton, Randall, Lastrup | Little Falls 2nne | May 4 | Oct 5 | 151 |
| Long Prairie | Eagle Bend, Browerville, Clarissa, Swanville | Long Prairie | May 13 | Sep 27 | 134 |
| Longville | — | Leech Lake | May 8 | Oct 1 | 144 |
| Mahtowa | Moose Lake, Rutledge, Denham | Moose Lake 1 Sse | May 12 | Oct 2 | 144 |
| Menahga | Sebeka | Park Rapids Muni Ap | May 14 | Sep 25 | 133 |
| Mentor | — | Red Lake Falls | May 9 | Sep 30 | 142 |
| Milaca | Foreston, Hillman, Gilman, Bock | Milaca | May 8 | Oct 1 | 143 |
| Miltona | Carlos | Alexandria Muni Ap | May 2 | Oct 8 | 159 |
| Mora | Brook Park, Ogilvie, Henriette | Mora | May 9 | Sep 30 | 142 |
| Nashua | Wendell, Tintah, Campbell | Wheaton | May 1 | Oct 9 | 160 |
| New Munich | Elrosa | Melrose | May 4 | Oct 1 | 148 |
| Ottertail | Perham, Henning, New York Mills, Battle Lake, Vining, Underwood, +3 more | Ottertail | May 5 | Oct 5 | 153 |
| Palisade | — | Sandy Lake Dam Libby | May 7 | Oct 3 | 148 |
| Pelican Rapids | Barnesville, Rothsay, Erhard, Elizabeth, Foxhome, Wolverton, +2 more | Rothsay | May 5 | Oct 3 | 149 |
| Pequot Lakes | Nisswa, Randall, Motley, Pillager | Gull Lake Dam | May 2 | Oct 6 | 156 |
| Pine * | Hinckley, Grantsburg | Grantsburg | May 11 | Oct 1 | 141 |
| Pine Point | — | Tamarac Wildlife Re | May 5 | Oct 3 | 150 |
| Rice | — | Rice | May 10 | Sep 29 | 140 |
| Rice Lake | — | Island Lake 4e | May 21 | Sep 27 | 129 |
| Silver Bay | Finland, Beaver Bay | Wolf Ridge Elc | May 15 | Oct 1 | 137 |
| St. Stephen | Bowlus | Collegeville St John's | May 3 | Oct 7 | 155 |
| Stanchfield | — | Cambridge | May 2 | Oct 4 | 153 |
| Taconite | Cohasset, Grand Rapids, Coleraine, Marble, Warba, Calumet, +2 more | Grand Rpds Forest Lab | May 17 | Sep 24 | 130 |
| Tamarack | McGregor, Cromwell, Wright, Kettle River | Wright 3 E | May 31 | Sep 18 | 107 |
| Taylors Falls | Milltown, Centuria, Center | Wild Rvr Sp | May 19 | Sep 25 | 128 |
| Thief River Falls | — | Thief Rvr Falls 2 | May 14 | Sep 28 | 135 |
| Wadena | Staples, Deer Creek, Bluffton, Hewitt, Parkers Prairie, Bertha, +2 more | Wadena 3 S | May 10 | Sep 30 | 141 |
| Walker | Akeley | Walker | May 4 | Oct 7 | 155 |
| Warba | Floodwood, Brookston | Floodwood 3 Ne | May 29 | Sep 18 | 111 |
* Pine is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Pine, representative)
Computed from Pine's average frost dates — the median-season location in this Minnesotazone 4a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Mar 16 – Mar 30 | May 18 – May 25 | Jul 17 – Aug 6 | — | matures comfortably |
| Pepper | Very tender | Mar 2 – Mar 16 | May 25 – Jun 1 | Jul 24 – Aug 23 | — | matures comfortably |
| Cucumber | Tender | Apr 13 – Apr 20 | May 18 – May 25 | Jul 7 – Jul 27 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 18 – May 25 | Jul 2 – Jul 17 | — | matures comfortably |
| Bush bean | Tender | — | May 18 – May 25 | Jul 7 – Jul 17 | Aug 2 – Aug 12 | matures comfortably |
| Sweet corn | Tender | — | May 11 – May 25 | Jul 10 – Aug 9 | — | matures comfortably |
| Basil | Very tender | Mar 30 – Apr 13 | May 18 – May 25 | Jun 17 – Jul 2 | — | matures comfortably |
| Lettuce | Half-hardy | Mar 30 – Apr 13 | Apr 13 – Apr 27 | May 28 – Jun 12 | Jul 19 – Aug 3 | matures comfortably |
| Pea | Hardy | — | Mar 30 – Apr 13 | May 24 – Jun 8 | Jul 9 – Jul 24 | matures comfortably |
| Spinach | Hardy | — | Mar 30 – Apr 13 | May 9 – May 19 | Jul 29 – Aug 8 | matures comfortably |
| Carrot | Half-hardy | — | Apr 20 – Apr 27 | Jun 19 – Jul 9 | Jun 29 – Jul 19 | matures comfortably |
| Broccoli | Half-hardy | Mar 16 – Mar 30 | Apr 13 – Apr 27 | Jun 7 – Jun 27 | Jul 4 – Jul 24 | matures comfortably |
Which crops fit this growing season
Using Pine's own 141-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Pine)
From NOAA's 1991–2020 Climate Normals at station USW00014995. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | May 23 | Jun 6 | Sep 22 | Oct 5 | 120 |
| 32°F (freeze) | May 11 | May 28 | Oct 1 | Oct 14 | 141 |
| 28°F | Apr 30 | May 17 | Oct 11 | Oct 26 | 161 |
| 24°F | Apr 19 | May 4 | Oct 22 | Nov 7 | 185 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 49 locations is 2,088; Pine's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,339 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,172 | cool-season crops (brassicas, greens) |
Hardiness zone 4a in Minnesota
Zone 4a means an average annual extreme minimum winter temperature of about −30 to −25 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Minnesota spans 5 hardiness zones in this dataset — see all Minnesota locations for the full range, including zones3a, 3b, 4b, 5a.
Explore zone 4a in other states at zone 4a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 4a mean in Minnesota?
- Zone 4a means an average annual extreme minimum winter temperature of −30 to −25 °F — the standard USDA measure of which perennials survive winter. 49 locations in Minnesota fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Minnesota's zone 4a is the growing season longest?
- Nashua runs the longest season on this page at about 160 days; Hibbing is shortest at about 93 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in Minnesota's zone 4a?
- Using Pine's frost dates (this page's median-season location): start seeds indoors about Mar 16 – Mar 30, then transplant outside about May 18 – May 25. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Minnesota's zone 4a have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 49 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.