Flint, Michigan: planting zone & frost dates
Flint is in USDA plant hardiness zone 6a, where the average coldest winter night reaches -10 to -5°F (-23.3 to -20.6°C). The typical last spring frost is around May 10 and the first fall frost around Oct 7.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 20 | Sep 30 |
| Typical planning date (30% risk) | May 10 | Oct 7 |
| Median (50%) | May 3 | Oct 13 |
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 FLINT 7W, MI (USC00202851), 4.0 mi (6.5 km) from the city center and 49 ft lower than the city center (-15 m). Record used for the 1991–2020 normals: 15 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Flint
All 7 ZIP codes covering Flint are in zone 6a.
Vegetable planting calendar for Flint
Dates are counted from the 30%-risk frost dates above (last frost May 10, first frost Oct 7). 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 15 – Mar 29 | May 17 – May 31 | — | — |
| Pepper | Mar 1 – Mar 15 | May 24 – Jun 7 | — | — |
| Lettuce | Mar 29 – Apr 12 | Apr 26 – May 17 | Apr 12 – May 24 | Jul 29 – Aug 26 |
| Green Beans | — | — | May 17 – Jun 21 | Jul 15 – Jul 29 |
| Sweet Corn | — | — | May 17 – Jun 14 | — |
| Zucchini & Summer Squash | Apr 12 – Apr 19 | May 17 – May 31 | May 17 – Jun 7 | Jul 15 – Jul 29 |
| Cucumber | Apr 12 – Apr 19 | May 24 – May 31 | May 17 – Jun 7 | Jul 15 – Jul 29 |
| Carrot | — | — | Apr 19 – May 24 | Jul 15 – Jul 29 |
| Onion | Feb 15 – Mar 1 | Apr 12 – Apr 26 | — | — |
| Potato | — | Apr 12 – May 3 | — | — |
| Basil | Mar 29 – Apr 12 | May 24 – Jun 7 | May 24 – Jun 14 | — |
| Spinach | — | — | Mar 29 – Apr 26 | Aug 12 – Sep 9 |
| Kale | Mar 15 – Mar 29 | Apr 12 – May 3 | Apr 12 – May 3 | Jul 29 – Aug 26 |
| Broccoli | Mar 15 – Mar 29 | Apr 26 – May 17 | — | Jul 15 – Jul 29 |
| Peas | — | — | Mar 29 – Apr 19 | Jul 29 – Aug 12 |
| Eggplant | Mar 1 – Mar 15 | May 24 – Jun 7 | — | — |
| Cabbage | Mar 15 – Mar 29 | Apr 12 – Apr 26 | — | Jul 15 – Jul 29 |
| Radish | — | — | Apr 5 – May 24 | Aug 26 – Sep 23 |
| Strawberry | — | Apr 12 – May 3 | — | — |
| Beets | — | — | Apr 19 – May 31 | Jul 29 – Aug 12 |
Nearby cities in Michigan
- Farmington Hills — zone 6a, last frost May 8, first frost Oct 10
- Rochester Hills — zone 6a, last frost May 2, first frost Oct 16
- Southfield — zone 6b, last frost May 8, first frost Oct 10
- Troy — zone 6b, last frost May 2, first frost Oct 16
- Livonia — zone 6b, last frost May 8, first frost Oct 10
- Ann Arbor — zone 6a, last frost May 11, first frost Oct 4
More: all Michigan cities · other zone 6a cities: Chicago, IL, Denver, CO, Milwaukee, WI, Colorado Springs, CO, Omaha, NE, Aurora, CO, Lincoln, NE, Fort Wayne, IN
Flint gardening questions
When is the last frost in Flint, MI?
Plan around May 10. At NOAA's Flint 7W, MI station, 4.0 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 3, and after May 20 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 22. The 90% and 10% dates are 30 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Flint, MI?
Start seeds indoors Mar 15 – Mar 29 and set transplants outside May 17 – May 31, once nights stay above 50°F and the soil is near 60°F. That leaves 150 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 Flint?
About 162 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 142 days, and in 1 year in 10 it runs 181 days or more. In fall there is a 10% chance of frost by Sep 30 and a 30% chance by Oct 7. That ranks 14th longest of 15 Michigan cities on this site.
When should I plant a fall garden in Flint?
Count back from the first fall frost (Oct 7): transplant broccoli Jul 15 – Jul 29; sow kale Jul 29 – Aug 26; sow lettuce Jul 29 – Aug 26; sow radishes Aug 26 – Sep 23. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 27. How the math works: succession and fall planting.
Did Flint's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Flint is zone 6a on both the 2012 and the 2023 USDA maps (PRISM/OSU ZIP listings). About 42% of U.S. ZIP codes kept their half-zone in 2023. Why the 2023 map is warmer.
How does Flint compare with Rochester Hills, MI?
Both are in zone 6a. The typical last spring frost in Flint (May 10) comes about 8 days later than in Rochester Hills, MI (May 2), 37 miles away, and the first fall frost is Oct 7 versus Oct 16. The two cities use different NOAA stations.