USDA zone 4b in Michigan
USDA plant hardiness zone 4b covers 16 locations across Michigan (average annual extreme minimum −25 to −20 °F): Bessemer, MI, Brimley, MI, Chatham, MI, Covington, MI, Indian River, MI, Kincheloe, MI, and 10 more. Average last spring frost across this group ranges May 9 (Sault Ste. Marie) to June 7 (Wolverine), and growing seasons run 95–151 days (Wolverine to Sault Ste. Marie) — 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 Mass, this group's median-season location.
- USDA zone
- 4b−25 to −20 °F
- Last frost range
- May 9–Jun 7avg, 32°F
- First frost range
- Sep 14–Oct 14avg, 32°F
- Growing season range
- 95–151days
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) |
|---|---|---|---|---|---|
| Bessemer | — | Ironwood | May 20 | Oct 1 | 132 |
| Brimley | — | Sault Ste Marie | May 22 | Oct 4 | 136 |
| Chatham | — | Munising | May 16 | Oct 14 | 148 |
| Covington | — | Watton 2wsw | May 25 | Sep 25 | 123 |
| Indian River | Brutus | Pellston Rgnl Ap | May 31 | Sep 18 | 108 |
| Kincheloe | — | Pickford 3ne | May 31 | Sep 25 | 116 |
| Kincheloe | — | Trout Lake 1sw | May 21 | Oct 1 | 131 |
| Mass * | Rockland | Ontonagon 6 Se | May 27 | Oct 1 | 127 |
| Norway | Iron Mountain | Iron Mtn Ford Ap | May 25 | Sep 24 | 121 |
| Norway | Kingsford, Niagara, Quinnesec, Pembine | Iron Mtn-kingsford Wwtp | May 17 | Oct 1 | 135 |
| Republic | Crystal Falls, Florence, Alpha, Long Lake | Florence | May 24 | Sep 25 | 121 |
| Sault Ste. Marie | Kincheloe | Sault Ste Marie Sanderson Fld | May 9 | Oct 11 | 151 |
| Watersmeet | Bruce Crossing | Paulding | May 31 | Sep 19 | 111 |
| West Ishpeming | Gwinn, Palmer | Marquette | May 22 | Sep 29 | 129 |
| White Pine | Bruce Crossing, Ewen, Bergland | Bergland Dam | May 26 | Sep 27 | 123 |
| Wolverine | Tower | Vanderbilt 11ene | Jun 7 | Sep 14 | 95 |
* Mass 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 (Mass, representative)
Computed from Mass's average frost dates — the median-season location in this Michiganzone 4b 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 | Apr 1 – Apr 15 | Jun 3 – Jun 10 | Aug 2 – Aug 22 | — | matures comfortably |
| Pepper | Very tender | Mar 18 – Apr 1 | Jun 10 – Jun 17 | Aug 9 – Sep 8 | — | matures comfortably |
| Cucumber | Tender | Apr 29 – May 6 | Jun 3 – Jun 10 | Jul 23 – Aug 12 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Jun 3 – Jun 10 | Jul 18 – Aug 2 | — | matures comfortably |
| Bush bean | Tender | — | Jun 3 – Jun 10 | Jul 23 – Aug 2 | Aug 2 – Aug 12 | matures comfortably |
| Sweet corn | Tender | — | May 27 – Jun 10 | Jul 26 – Aug 25 | — | matures comfortably |
| Basil | Very tender | Apr 15 – Apr 29 | Jun 3 – Jun 10 | Jul 3 – Jul 18 | — | matures comfortably |
| Lettuce | Half-hardy | Apr 15 – Apr 29 | Apr 29 – May 13 | Jun 13 – Jun 28 | Jul 19 – Aug 3 | matures comfortably |
| Pea | Hardy | — | Apr 15 – Apr 29 | Jun 9 – Jun 24 | Jul 9 – Jul 24 | matures comfortably |
| Spinach | Hardy | — | Apr 15 – Apr 29 | May 25 – Jun 4 | Jul 29 – Aug 8 | matures comfortably |
| Carrot | Half-hardy | — | May 6 – May 13 | Jul 5 – Jul 25 | Jun 29 – Jul 19 | matures comfortably |
| Broccoli | Half-hardy | Apr 1 – Apr 15 | Apr 29 – May 13 | Jun 23 – Jul 13 | Jul 4 – Jul 24 | matures comfortably |
Which crops fit this growing season
Using Mass's own 127-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 (Mass)
From NOAA's 1991–2020 Climate Normals at station USC00206220. 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 | Jun 8 | Jul 1 | Sep 17 | Oct 3 | 98 |
| 32°F (freeze) | May 27 | Jun 13 | Oct 1 | Oct 16 | 127 |
| 28°F | May 10 | May 29 | Oct 14 | Nov 1 | 157 |
| 24°F | Apr 28 | May 14 | Oct 31 | Nov 11 | 184 |
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 16 locations is 1,742; Mass's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,020 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 3,803 | cool-season crops (brassicas, greens) |
Hardiness zone 4b in Michigan
Zone 4b means an average annual extreme minimum winter temperature of about −25 to −20 °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, 5a, 5b, 6a, 6b, 7a.
Explore zone 4b in other states at zone 4b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 4b mean in Michigan?
- Zone 4b means an average annual extreme minimum winter temperature of −25 to −20 °F — the standard USDA measure of which perennials survive winter. 16 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 4b is the growing season longest?
- Sault Ste. Marie runs the longest season on this page at about 151 days; Wolverine is shortest at about 95 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 4b?
- Using Mass's frost dates (this page's median-season location): start seeds indoors about Apr 1 – Apr 15, then transplant outside about Jun 3 – Jun 10. 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 4b 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 16 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.