Frost dates for Detroit, Michigan
In Detroit, half of springs have had their last frost by April 21 (and 1 spring in 10 still has one after May 6), and half of falls have had their first frost by October 31, leaving about 190 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Detroit, Michigan
Last spring frost
April 21
Half of springs have their last frost by this date. For a safer bet, wait until May 6: only 1 spring in 10 has a frost after that.
First fall frost
October 31
Half of falls have their first frost by this date. In 1 fall in 10 it comes by October 17.
Growing season
190 days
Frost-free days in a typical year. 9 years in 10 get at least 171.
Hardiness zone
6b
2023 USDA map: the coldest night of winter averages −5°F to 0°F. It was 6b on the 2012 map too. All 25 ZIP codes within about 6 miles of the city's center are in zone 6b.
Stations near you disagree. NOAA's Detroit City Airport (5 miles away, at 630 feet above sea level), the one we used, gives a typical last frost of April 21 and a typical first frost of October 31. NOAA's Dearborn (8 miles away, at 600 feet above sea level) gives a typical last frost of May 1 and a typical first frost of October 15. So the typical last frost could fall anywhere from April 21 to May 1 and the typical first frost from October 15 to 31, depending on whether your garden is more like one or the other. Local terrain matters: hillsides, valley floors, water and city heat can change frost dates a lot over a few miles. Treat the dates here as a starting point, and compare with a nearby gardener or your county extension office.
Print a year planner for Detroit
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | April 7 | April 21 | May 6 |
| First frost in fall | October 17 | October 31 | November 11 |
The frost-free season between them runs 190 days in a typical year. In 1 year in 10 it is 208 days or longer, and in 1 year in 10 it is 171 days or shorter.
- Hard freeze (28°F): typically last on April 8 and first on November 9. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on May 1 and first on October 18. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Detroit comes between April 7 and May 6, a window of 29 days. That is about average for NOAA's stations (the typical window is 31 days).
Among Michigan's 211 NOAA stations with a frost every year, 98 percent have their typical last frost later than Detroit does.
Planting calendar for Detroit
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
| When | What to do | Why then |
|---|---|---|
| February | ||
| February 3 to March 3 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| February 17 to March 17 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| March | ||
| March 3 to 24 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| March 10 to 24 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| March 17 to 31 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| March 24 to April 7 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 24 to April 7 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| April | ||
| April 7 to 21 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| April 7 to 21 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| April 21 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| May | ||
| May 5 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| May 5 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| June | ||
| June 5 to 19 | Cabbage for fall Start seeds | set the plants out by July 24 |
| June 25 to July 9 | Broccoli for fall Start seeds | set the plants out by August 13 |
| August | ||
| August 4 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 8 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| August 9 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 13 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| August 14 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 18 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| August 28 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 7 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| September 17 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 17 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| November | ||
| November 16 to 23 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 15 days later. That plans around May 6, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Detroit City Airport (station USW00014822), 5 miles from the center of Detroit. It sits at about the same elevation, 630 feet above sea level. NOAA rates this station's record as standard: at least 24 of the 30 years, with gaps filled from nearby stations.
The same station also gives the frost dates for Warren, Troy, St. Clair Shores, Royal Oak, Roseville, Eastpointe, Oak Park and Madison Heights.
Our ZIP code lookup matches these 29 ZIP codes to the same station, so they get the same dates: 48015, 48017, 48030, 48067, 48069, 48070, 48071, 48083, 48088, 48089, 48091, 48092, 48093, 48201, 48202, 48203, 48205, 48207, 48211, 48212, 48213, 48214, 48215, 48220, 48226, 48234, 48243, 48310, 48312. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- Sterling Heights, Michigan: last frost around April 30, first frost around October 24 (15 miles away)
- Ann Arbor, Michigan: last frost around May 8, first frost around October 4 (35 miles away)
- Toledo, Ohio: last frost around April 20, first frost around October 27 (55 miles away)
See frost dates across Michigan, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.