When to plant in Flat Rock, MI
USDA Zone 6bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Flat Rock, Michigan — all computed from Flat Rock's nearest NOAA weather station.
Zone 6b means Flat Rock sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
CARLETON 2W · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Flat Rock’s own odds, recorded at CARLETON 2W.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 22 | May 6 | Apr 22 | Sep 23 | Oct 6 | Oct 21 |
| 32°F | May 13 | Apr 27 | Apr 12 | Oct 4 | Oct 20 | Nov 2 |
| 28°F | May 2 | Apr 15 | Mar 31 | Oct 17 | Nov 1 | Nov 14 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Flat Rock, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 16 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Flat Rock planting FAQ
When is the last spring frost in Flat Rock, MI?
Flat Rock's average last spring frost falls near April 27 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Flat Rock, MI?
In Flat Rock, the first 32°F freeze of fall lands around October 20 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Flat Rock in?
Flat Rock is in USDA hardiness zone 6b. In zone 6b, winters are moderate — most common vegetables grow well in season.
How long is the growing season in Flat Rock?
There are roughly 176 frost-free days in Flat Rock (a moderate growing season), running from the average last frost around April 27 to the first fall frost near October 20.
When should I plant tomatoes in Flat Rock?
In Flat Rock, start tomato seeds indoors around March 2–March 16, then transplant seedlings outdoors around May 4 once the danger of frost has passed.
Never miss a window in Flat Rock
An email when it’s time to start seeds, transplant, and sow — timed to Flat Rock’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at CARLETON 2W, 14 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Flat Rock, MI — Frost Dates & Zone 6b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00201250. Retrieved from https://blissgarden.com/michigan/flat-rock.