Troy, Michigan: planting zone & frost dates
Troy 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 2 and the first fall frost around Oct 16.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 12 | Oct 7 |
| Typical planning date (30% risk) | May 2 | Oct 16 |
| Median (50%) | Apr 26 | Oct 22 |
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 PONTIAC WWTP, MI (USC00206658), 6.8 mi (10.9 km) from the city center and 207 ft higher than the city center (+63 m). Record used for the 1991–2020 normals: 15 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Troy
All 4 ZIP codes covering Troy are in zone 6b.
Vegetable planting calendar for Troy
Dates are counted from the 30%-risk frost dates above (last frost May 2, first frost Oct 16). 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 7 – Mar 21 | May 9 – May 23 | — | — |
| Pepper | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Lettuce | Mar 21 – Apr 4 | Apr 18 – May 9 | Apr 4 – May 16 | Aug 7 – Sep 4 |
| Green Beans | — | — | May 9 – Jun 13 | Jul 24 – Aug 7 |
| Sweet Corn | — | — | May 9 – Jun 6 | — |
| Zucchini & Summer Squash | Apr 4 – Apr 11 | May 9 – May 23 | May 9 – May 30 | Jul 24 – Aug 7 |
| Cucumber | Apr 4 – Apr 11 | May 16 – May 23 | May 9 – May 30 | Jul 24 – Aug 7 |
| Carrot | — | — | Apr 11 – May 16 | Jul 24 – Aug 7 |
| Onion | Feb 7 – Feb 21 | Apr 4 – Apr 18 | — | — |
| Potato | — | Apr 4 – Apr 25 | — | — |
| Basil | Mar 21 – Apr 4 | May 16 – May 30 | May 16 – Jun 6 | — |
| Spinach | — | — | Mar 21 – Apr 18 | Aug 21 – Sep 18 |
| Kale | Mar 7 – Mar 21 | Apr 4 – Apr 25 | Apr 4 – Apr 25 | Aug 7 – Sep 4 |
| Broccoli | Mar 7 – Mar 21 | Apr 18 – May 9 | — | Jul 24 – Aug 7 |
| Peas | — | — | Mar 21 – Apr 11 | Aug 7 – Aug 21 |
| Eggplant | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Cabbage | Mar 7 – Mar 21 | Apr 4 – Apr 18 | — | Jul 24 – Aug 7 |
| Radish | — | — | Mar 28 – May 16 | Sep 4 – Oct 2 |
| Strawberry | — | Apr 4 – Apr 25 | — | — |
| Beets | — | — | Apr 11 – May 23 | Aug 7 – Aug 21 |
Nearby cities in Michigan
- Rochester Hills — zone 6a, last frost May 2, first frost Oct 16
- Sterling Heights — zone 6b, last frost May 5, first frost Oct 18
- Warren — zone 6b, last frost Apr 27, first frost Oct 24
- Southfield — zone 6b, last frost May 8, first frost Oct 10
- Detroit — zone 6b, last frost May 2, first frost Oct 20
- Farmington Hills — zone 6a, last frost May 8, first frost Oct 10
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
Troy gardening questions
When is the last frost in Troy, MI?
Plan around May 2. At NOAA's Pontiac Wwtp, MI station, 6.8 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 Apr 26, and after May 12 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 16. The last frost is fairly predictable here: only 27 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Troy, MI?
Start seeds indoors Mar 7 – Mar 21 and set transplants outside May 9 – May 23, once nights stay above 50°F and the soil is near 60°F. That leaves 167 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 Troy?
About 177 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 158 days, and in 1 year in 10 it runs 195 days or more. In fall there is a 10% chance of frost by Oct 7 and a 30% chance by Oct 16. That ranks 4th longest of 15 Michigan cities on this site.
When should I plant a fall garden in Troy?
Count back from the first fall frost (Oct 16): transplant broccoli Jul 24 – Aug 7; sow kale Aug 7 – Sep 4; sow lettuce Aug 7 – Sep 4; sow radishes Sep 4 – Oct 2. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 4. How the math works: succession and fall planting.
Did Troy's hardiness zone change on the 2023 map?
Yes. Most of Troy 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 Troy compare with Sterling Heights, MI?
Both are in zone 6b. The typical last spring frost in Troy (May 2) comes about the same time as in Sterling Heights, MI (May 5), 6 miles away, and the first fall frost is Oct 16 versus Oct 18. The two cities use different NOAA stations.