USDA zone 6a in Michigan
USDA plant hardiness zone 6a covers 83 locations across Michigan (average annual extreme minimum −10 to −5 °F): Adrian, MI, Allegan, MI, Allendale, MI, Alma, MI, Ann Arbor, MI, Ann Arbor, MI, and 77 more. Average last spring frost across this group ranges April 19 (Marysville) to May 24 (Rapid), and growing seasons run 128–196 days (Rapid to Marysville) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Michigan location's own frost dates; the printable planting calendar uses Coldwater, this group's median-season location.
- USDA zone
- 6a−10 to −5 °F
- Last frost range
- Apr 19–May 24avg, 32°F
- First frost range
- Sep 28–Nov 3avg, 32°F
- Growing season range
- 128–196days
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) |
|---|---|---|---|---|---|
| Adrian | Manitou Beach-Devils Lake, Jasper, Hudson, Morenci, Addison, Clayton, +1 more | Adrian Lenawee Co Ap | Apr 27 | Oct 20 | 173 |
| Allegan | Paw Paw, Otsego, Bangor, Bloomingdale, Fennville, Gobles, +1 more | Bloomingdale | May 7 | Oct 11 | 156 |
| Allendale | Hudsonville, Dorr, Zeeland, Fennville | Holland Tulip City Ap | Apr 28 | Oct 21 | 175 |
| Alma | Ithaca, St. Louis, Crystal, Elm Hall, Carson, Breckenridge, +2 more | Alma | May 1 | Oct 13 | 164 |
| Ann Arbor | Saline, Ypsilanti, Milan, Dexter | Ann Arbor Muni Ap | May 8 | Oct 4 | 147 |
| Ann Arbor | Whitmore Lake, Ypsilanti, Plymouth, Northville, Barton Hills | Ann Arbor U Of Mich | May 3 | Oct 13 | 160 |
| Au Gres | Pinconning | Standish 4ne | May 5 | Oct 10 | 156 |
| Battle Creek | Marshall, Level Park-Oak Park, Brownlee Park, Galesburg, Climax, Augusta, +2 more | Battle Creek Kellogg Ap | Apr 30 | Oct 19 | 170 |
| Bay | Shields, Freeland, Hemlock, Zilwaukee, St. Charles, Auburn | Saginaw Mbs Intl Ap | Apr 26 | Oct 17 | 172 |
| Bay | Robin Glen-Indiantown, Essexville | Essexville | Apr 27 | Oct 20 | 173 |
| Bay Port | Bad Axe, Ubly, Kinde, Elkton, Pigeon, Owendale | Bad Axe | May 5 | Oct 19 | 163 |
| Caro | Sebewaing, Clifford, Millington, Reese, Fairgrove, Mayville, +3 more | Caro Wwtp | May 7 | Oct 9 | 154 |
| Caseville | — | Filion 5nnw | May 8 | Oct 17 | 162 |
| Charlevoix | — | Charlevoix | May 1 | Oct 28 | 178 |
| Charlotte | Eaton Rapids, Potterville, Vermontville, Springport, Mulliken, Olivet, +1 more | Charlotte | May 1 | Oct 15 | 164 |
| Chelsea | Dexter, Stockbridge, Grass Lake | Chelsea | Apr 30 | Oct 12 | 163 |
| Coldwater * | Quincy, Union, Homer, Bronson, Sherwood, Tekonsha, +1 more | Coldwater St School | May 2 | Oct 13 | 163 |
| Coleman | Beaverton, Pinconning | Gladwin | May 9 | Oct 4 | 148 |
| Coopersville | Wolf Lake, Twin Lake, Nunica, Ravenna | Muskegon Co Ap | Apr 30 | Oct 19 | 170 |
| Copper Harbor | — | Copper Harbor Ft Wilkins | May 20 | Oct 15 | 148 |
| Croswell | Lexington, Applegate, Port Sanilac | Lexington Wtp | May 4 | Oct 24 | 171 |
| Custer | Free Soil, Fountain | Manistee 3se | May 14 | Oct 12 | 151 |
| Dowagiac | Cassopolis, Lawrence, Decatur, Edwardsburg | Dowagiac 1 W | May 4 | Oct 11 | 158 |
| Dowling | Hastings, Middleville, Delton, Nashville, Woodland, Freeport, +1 more | Hastings | May 3 | Oct 12 | 158 |
| Dundee | Ida, Maybee, Petersburg | Dundee | Apr 27 | Oct 21 | 176 |
| Durand | Vernon, Lennon, Byron, Bancroft | Durand Wwtp | May 3 | Oct 11 | 159 |
| Eastport | Central Lake | E Jordan | May 23 | Oct 2 | 131 |
| Elk Rapids | — | Nw Michigan Rsch Farm | Apr 30 | Nov 1 | 182 |
| Farmington Hills | Novi | Farmington | May 1 | Oct 17 | 165 |
| Flint | Burton, Beecher, Swartz Creek, Grand Blanc, Flushing, Argentine, +4 more | Flint Bishop Intl Ap | May 6 | Oct 10 | 155 |
| Forest Hills | Grand Rapids, Wyoming, Walker, Kentwood, Northview, Grandville, +10 more | Grand Rapids | Apr 29 | Oct 20 | 174 |
| Fowlerville | — | Howell Wwtp | May 4 | Oct 7 | 156 |
| Frankenmuth | Birch Run | Frankenmuth 1se | May 3 | Oct 12 | 161 |
| Goodrich | Ortonville | Goodrich | May 1 | Oct 14 | 164 |
| Greenville | Cedar Springs, Sheridan, Trufant, Sand Lake | Greenville 2 Nne | May 18 | Sep 28 | 133 |
| Harbor Beach | Minden, Forestville | Harbor Beach 1 Sse | May 2 | Oct 24 | 173 |
| Hart | Shelby, Custer | Hart 3 Wsw | May 12 | Oct 10 | 151 |
| Hartford | Berrien Springs, Eau Claire | Eau Claire 4 Ne | Apr 22 | Oct 30 | 189 |
| Hillsdale | Jonesville, Litchfield, Pittsford, Lake LeAnn, Reading, Waldron, +4 more | Hillsdale | May 3 | Oct 12 | 161 |
| Honor | — | Frankfort 2ne | May 2 | Oct 26 | 175 |
| Hopkins | — | Allegan 5ne | May 4 | Oct 15 | 160 |
| Ionia | Belding, Portland, Hubbardston, Lyons, Saranac, Pewamo, +5 more | Ionia 2ssw | May 3 | Oct 12 | 161 |
| Jackson | Michigan Center, Vandercook Lake, Albion, Spring Arbor, Napoleon, Stockbridge, +5 more | Jackson Reynolds Fld | May 1 | Oct 14 | 164 |
| Kaleva | Thompsonville, Bear Lake | Beulah 7ssw | May 7 | Oct 20 | 163 |
| Lake Ann | — | Maple City 1e | May 22 | Oct 9 | 140 |
| Lansing | Haslett, East Lansing, Waverly, Bath, Grand Ledge, DeWitt, +3 more | Lansing Capital City Ap | May 1 | Oct 13 | 162 |
| Lapeer | Attica, Fostoria, Imlay, Davison, North Branch, Almont, +7 more | Lapeer Wwtp | May 4 | Oct 14 | 160 |
| Lost Lake Woods | Harrisville | Harrisville 2nne | May 8 | Oct 16 | 160 |
| Marysville | Ruby, St. Clair, Marine, Lakeport | Port Huron | Apr 19 | Nov 3 | 196 |
| Midland | Sanford, Auburn, Pinconning, Merrill | Midland | Apr 29 | Oct 16 | 167 |
| Montague | Rothbury | Montague 4 Nw | May 19 | Oct 4 | 136 |
| Mount Pleasant | Shepherd, Rosebush | Central Michigan Univ | Apr 30 | Oct 20 | 171 |
| Napoleon | Vineyard Lake, Manchester, Clinton | Manchester | Apr 30 | Oct 14 | 165 |
| Novi | Wixom, Fenton, Howell, Whitmore Lake, South Lyon, Brighton, +3 more | Milford Gm Proving Ground | May 6 | Oct 12 | 157 |
| Okemos | Holt, Mason, Williamston, Webberville, Dansville | East Lansing 4 S | Apr 28 | Oct 17 | 173 |
| Ossineke | — | Alpena Wwtp | May 5 | Oct 17 | 163 |
| Owosso | Henderson, Corunna, Chesaning, Perry, St. Charles, Laingsburg, +3 more | Owosso Wwtp | May 1 | Oct 15 | 164 |
| Pinckney | — | Hell | Apr 30 | Oct 14 | 166 |
| Plainwell | Hickory Corners, Richland | Gull Lake Biological Stn | Apr 29 | Oct 20 | 173 |
| Port Austin | — | Port Austin Wwtp | May 4 | Oct 26 | 172 |
| Port Hope | — | Port Hope | May 5 | Oct 24 | 169 |
| Portage | Kalamazoo, Mattawan, Comstock Northwest, Vicksburg, Westwood, Eastwood, +1 more | Kalamazoo Battle Ck Intl Ap | Apr 28 | Oct 18 | 172 |
| Presque Isle Harbor | — | Alpena Co Rgnl Ap | May 17 | Oct 1 | 136 |
| Rapid | — | Kalkaska | May 24 | Oct 1 | 128 |
| Rapid | Greilickville, Chums Corner, Bendon, Grawn | Traverse City Cherry Cptl Ap | May 12 | Oct 16 | 155 |
| Richmond | Romeo, Capac, Emmett, Memphis, Armada | Richmond 4 Nnw | May 1 | Oct 20 | 170 |
| Rochester | Richmond, New Haven, Romeo, Utica | Mt Clemens Ang Base | Apr 30 | Oct 24 | 174 |
| Rochester Hills | Pontiac, Auburn Hills, Bloomfield Hills, Rochester, Holly, Milford, +9 more | Pontiac Oakland Co Intl Ap | Apr 29 | Oct 20 | 172 |
| Rogers | — | Rogers City | May 10 | Oct 14 | 154 |
| Saginaw | Bridgeport, Shields, Burt, Buena Vista, Zilwaukee | Saginaw #3 | Apr 29 | Oct 21 | 175 |
| Scottville | — | Ludington 4 Se | May 17 | Oct 7 | 144 |
| Snover | Sandusky, Marlette, Deckerville, Carsonville, Peck | Sandusky | May 2 | Oct 16 | 165 |
| Snover | Cass, Gagetown | Cass City 1 Ssw | May 7 | Oct 10 | 152 |
| Sparta | Kent, Ravenna, Casnovia, Grant | Kent City 2 Sw | May 14 | Sep 29 | 135 |
| St. James | — | St James 4ssw Beaver | May 11 | Oct 19 | 159 |
| St. Johns | Maple Rapids, Fowler, Elsie, Westphalia, Ovid, Ashley, +1 more | Saint Johns | Apr 28 | Oct 24 | 179 |
| Sturgis | Three Rivers, Lawton, Constantine, Centreville, White Pigeon, Colon, +5 more | Three Rivers | Apr 30 | Oct 17 | 170 |
| Tecumseh | Blissfield, Onsted, Deerfield, Britton | Adrian 2 Nne | May 1 | Oct 15 | 164 |
| Twin Lake | — | Hesperia 4 Wnw | May 17 | Oct 1 | 137 |
| Vassar | — | Vassar | May 9 | Oct 7 | 150 |
| Watervliet | — | Benton Harbor Ap | May 5 | Oct 15 | 161 |
| Wayne | Belleville | Detroit Metro Ap | Apr 20 | Oct 27 | 188 |
| Yale | Melvin | Yale 1 Nnw | May 12 | Oct 5 | 147 |
* Coldwater 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 (Coldwater, representative)
Computed from Coldwater's average frost dates — the median-season location in this Michiganzone 6a 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 7 – Mar 21 | May 9 – May 16 | Jul 8 – Jul 28 | — | matures comfortably |
| Pepper | Very tender | Feb 21 – Mar 7 | May 16 – May 23 | Jul 15 – Aug 14 | — | matures comfortably |
| Cucumber | Tender | Apr 4 – Apr 11 | May 9 – May 16 | Jun 28 – Jul 18 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 9 – May 16 | Jun 23 – Jul 8 | — | matures comfortably |
| Bush bean | Tender | — | May 9 – May 16 | Jun 28 – Jul 8 | Aug 14 – Aug 24 | matures comfortably |
| Sweet corn | Tender | — | May 2 – May 16 | Jul 1 – Jul 31 | — | matures comfortably |
| Basil | Very tender | Mar 21 – Apr 4 | May 9 – May 16 | Jun 8 – Jun 23 | — | matures comfortably |
| Lettuce | Half-hardy | Mar 21 – Apr 4 | Apr 4 – Apr 18 | May 19 – Jun 3 | Jul 31 – Aug 15 | matures comfortably |
| Pea | Hardy | — | Mar 21 – Apr 4 | May 15 – May 30 | Jul 21 – Aug 5 | matures comfortably |
| Spinach | Hardy | — | Mar 21 – Apr 4 | Apr 30 – May 10 | Aug 10 – Aug 20 | matures comfortably |
| Carrot | Half-hardy | — | Apr 11 – Apr 18 | Jun 10 – Jun 30 | Jul 11 – Jul 31 | matures comfortably |
| Broccoli | Half-hardy | Mar 7 – Mar 21 | Apr 4 – Apr 18 | May 29 – Jun 18 | Jul 16 – Aug 5 | matures comfortably |
Which crops fit this growing season
Using Coldwater's own 163-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 (Coldwater)
From NOAA's 1991–2020 Climate Normals at station USC00201675. 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 14 | May 29 | Oct 2 | Oct 15 | 141 |
| 32°F (freeze) | May 2 | May 18 | Oct 13 | Oct 30 | 163 |
| 28°F | Apr 21 | May 8 | Oct 28 | Nov 9 | 187 |
| 24°F | Apr 9 | Apr 24 | Nov 7 | Nov 23 | 213 |
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 83 locations is 2,545; Coldwater's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,638 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,694 | cool-season crops (brassicas, greens) |
Hardiness zone 6a in Michigan
Zone 6a means an average annual extreme minimum winter temperature of about −10 to −5 °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. Michigan spans 7 hardiness zones in this dataset — see all Michigan locations for the full range, including zones4a, 4b, 5a, 5b, 6b, 7a.
Explore zone 6a in other states at zone 6a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 6a mean in Michigan?
- Zone 6a means an average annual extreme minimum winter temperature of −10 to −5 °F — the standard USDA measure of which perennials survive winter. 83 locations in Michigan fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Michigan's zone 6a is the growing season longest?
- Marysville runs the longest season on this page at about 196 days; Rapid is shortest at about 128 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 Michigan's zone 6a?
- Using Coldwater's frost dates (this page's median-season location): start seeds indoors about Mar 7 – Mar 21, then transplant outside about May 9 – May 16. 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 Michigan's zone 6a 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 83 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.