Dearborn, Michigan: planting zone & frost dates
Dearborn is in USDA plant hardiness zone 6b, where the average coldest winter night reaches -5 to 0°F (-20.6 to -17.8°C). The typical last spring frost is around May 8 and the first fall frost around Oct 9.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 18 | Oct 1 |
| Typical planning date (30% risk) | May 8 | Oct 9 |
| Median (50%) | May 1 | Oct 15 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station DEARBORN, MI (USC00202015), 1.4 mi (2.3 km) from the city center and 7 ft higher than the city center (+2 m). Record used for the 1991–2020 normals: 25 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Dearborn
All 4 ZIP codes covering Dearborn are in zone 6b.
Vegetable planting calendar for Dearborn
Dates are counted from the 30%-risk frost dates above (last frost May 8, first frost Oct 9). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 13 – Mar 27 | May 15 – May 29 | — | — |
| Pepper | Feb 27 – Mar 13 | May 22 – Jun 5 | — | — |
| Lettuce | Mar 27 – Apr 10 | Apr 24 – May 15 | Apr 10 – May 22 | Jul 31 – Aug 28 |
| Green Beans | — | — | May 15 – Jun 19 | Jul 17 – Jul 31 |
| Sweet Corn | — | — | May 15 – Jun 12 | — |
| Zucchini & Summer Squash | Apr 10 – Apr 17 | May 15 – May 29 | May 15 – Jun 5 | Jul 17 – Jul 31 |
| Cucumber | Apr 10 – Apr 17 | May 22 – May 29 | May 15 – Jun 5 | Jul 17 – Jul 31 |
| Carrot | — | — | Apr 17 – May 22 | Jul 17 – Jul 31 |
| Onion | Feb 13 – Feb 27 | Apr 10 – Apr 24 | — | — |
| Potato | — | Apr 10 – May 1 | — | — |
| Basil | Mar 27 – Apr 10 | May 22 – Jun 5 | May 22 – Jun 12 | — |
| Spinach | — | — | Mar 27 – Apr 24 | Aug 14 – Sep 11 |
| Kale | Mar 13 – Mar 27 | Apr 10 – May 1 | Apr 10 – May 1 | Jul 31 – Aug 28 |
| Broccoli | Mar 13 – Mar 27 | Apr 24 – May 15 | — | Jul 17 – Jul 31 |
| Peas | — | — | Mar 27 – Apr 17 | Jul 31 – Aug 14 |
| Eggplant | Feb 27 – Mar 13 | May 22 – Jun 5 | — | — |
| Cabbage | Mar 13 – Mar 27 | Apr 10 – Apr 24 | — | Jul 17 – Jul 31 |
| Radish | — | — | Apr 3 – May 22 | Aug 28 – Sep 25 |
| Strawberry | — | Apr 10 – May 1 | — | — |
| Beets | — | — | Apr 17 – May 29 | Jul 31 – Aug 14 |
Nearby cities in Michigan
- Detroit — zone 6b, last frost May 2, first frost Oct 20
- Southfield — zone 6b, last frost May 8, first frost Oct 10
- Westland — zone 6b, last frost Apr 28, first frost Oct 22
- Livonia — zone 6b, last frost May 8, first frost Oct 10
- Farmington Hills — zone 6a, last frost May 8, first frost Oct 10
- Warren — zone 6b, last frost Apr 27, first frost Oct 24
More: all Michigan cities · other zone 6b cities: Columbus, OH, Indianapolis, IN, Boston, MA, Detroit, MI, Kansas City, MO, Cincinnati, OH, Pittsburgh, PA, Buffalo, NY
Dearborn gardening questions
When is the last frost in Dearborn, MI?
Plan around May 8. At NOAA's Dearborn, MI station, 1.4 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by May 1, and after May 18 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 20. The 90% and 10% dates are 31 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Dearborn, MI?
Start seeds indoors Mar 13 – Mar 27 and set transplants outside May 15 – May 29, once nights stay above 50°F and the soil is near 60°F. That leaves 154 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Dearborn?
About 166 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 147 days, and in 1 year in 10 it runs 186 days or more. In fall there is a 10% chance of frost by Oct 1 and a 30% chance by Oct 9. That ranks 9th longest of 15 Michigan cities on this site.
When should I plant a fall garden in Dearborn?
Count back from the first fall frost (Oct 9): transplant broccoli Jul 17 – Jul 31; sow kale Jul 31 – Aug 28; sow lettuce Jul 31 – Aug 28; sow radishes Aug 28 – Sep 25. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 28. How the math works: succession and fall planting.
Did Dearborn's hardiness zone change on the 2023 map?
Yes. Most of Dearborn was zone 6a on the 2012 map and is zone 6b on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
How does Dearborn compare with Detroit, MI?
Both are in zone 6b. The typical last spring frost in Dearborn (May 8) comes about 6 days later than in Detroit, MI (May 2), 7 miles away, and the first fall frost is Oct 9 versus Oct 20. The two cities use different NOAA stations.