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Frost dates and planting calendar for Detroit, Michigan

Updated October 30, 2026. Based on USDA, NOAA and Colorado State University Extension data. Published by Humblebee.

USDA hardiness zone
6b[1]
Median last spring frost
Apr 21[2]
Median first fall frost
Oct 31[3]
Growing season, median
190 days[4]

Detroit sits in USDA hardiness zone 6b[1]. In half of years the last spring frost comes after April 21, the median date[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 7, half of years Apr 21, 1 in 10 years after May 6Last frostmedian Apr 21First fall frost: 9 in 10 years before Nov 11, half of years Oct 31, 1 in 10 years before Oct 17First frostmedian Oct 31Frost riskHardyHardy vegetables: plant Mar 24 to Apr 7Mar 24 to Apr 7Semi-hardySemi-hardy vegetables: plant Apr 7 to Apr 21Apr 7 to Apr 21TenderTender vegetables: plant around Apr 21around Apr 21Very tenderVery tender vegetables: plant from May 5from May 5
Shaded: the span between the dates frost passes in 9 of 10 years and 1 of 10 years[2][3]. Green: planting windows from the CSU rules applied to the median last frost (GardenFacts calculation)[6]. Exact dates are in the tables below.

These frost dates come from NOAA climate normals for the Detroit City Airport weather station, using records from 1991 to 2020[5]. They are chances, not promises. In half of years the last spring frost comes after April 21, and in 1 of 10 years it comes after May 6[2]. In fall, the median first frost is October 31, and in 1 of 10 years the first frost comes before October 17[3]. Any year can be earlier or later than these dates.

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 7 after April 21 after May 6
First fall frost (32°F)[3] before October 17 before October 31 before November 11
  • Hard freeze (28°F): median last spring date April 8, median first fall date November 9[7].
  • Frost-free growing season: at least 171 days in 9 of 10 years, 190 days in half of years and 208 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 100% of years[8].
  • Weather station: Detroit City Airport (USW00014822), 5 miles from the city center, 626 feet, 29 years of 1991 to 2020 records[5].

When to plant vegetables

The planting dates here use Colorado State University Extension's vegetable guide, which was written for Colorado[6]. GardenFacts takes the NOAA median last frost, April 21, as the average last frost[6]. Hardy crops like peas, lettuce and spinach can go in as early as March 24 to April 7[6]. Snap beans, sweet corn and cucumbers go in from seed around April 21[9]. Very tender crops like tomatoes and peppers typically wait 2 or more weeks after the median last frost, so their earliest start is May 5[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 21) is March 24 to April 7[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 21) is April 7, up to the median date itself[11]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 21[9]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 21), is May 5[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 24 May 28 (from transplants)
Cabbage (hardy)[12] Mar 24 Jun 17 (from transplants)
Kohlrabi (hardy)[12] Mar 24 May 13
Lettuce (hardy)[12] Mar 24 May 23
Onions (hardy)[12] Mar 24 Jul 12
Peas (hardy)[12] Mar 24 May 28
Radishes (hardy)[12] Mar 24 Apr 23
Spinach (hardy)[12] Mar 24 May 3
Turnips (hardy)[12] Mar 24 May 13
Beets (semi-hardy)[12] Apr 7 Jun 6
Carrots (semi-hardy)[12] Apr 7 Jun 16
Cauliflower (semi-hardy)[12] Apr 7 not listed
Parsnips (semi-hardy)[12] Apr 7 Jun 16
Potatoes (semi-hardy)[12] Apr 7 Aug 10
Swiss chard (semi-hardy)[12] Apr 7 Jun 6
Snap beans (tender)[12] Apr 21 Jun 20
Sweet corn (tender)[12] Apr 21 Jun 20
Cucumbers (tender)[12] Apr 21 Jun 15
Summer squash (tender)[12] Apr 21 Jun 10
Cantaloupe (very tender)[12] May 5 Jul 29
Eggplant (very tender)[12] May 5 Jul 4 (from transplants)
Peppers (very tender)[12] May 5 Jul 14 (from transplants)
Tomatoes (very tender)[12] May 5 Jul 9 (from transplants)
Winter squash (very tender)[12] May 5 Aug 13
Watermelon (very tender)[12] May 5 Jul 29
Spacing, depth and soil temperature (CSU Extension)
Vegetable Min. soil temp Depth Spacing Days to harvest
Broccoli[13] 40°F 1/2 in 18 in 65
Cabbage[13] 40°F 1/2 in 18 in 85
Kohlrabi[13] 40°F 1/2 in 7-9 in 50
Lettuce[13] 35°F 1/4 in 7-9 in 60
Onions[13] 35°F 1/4 in (seed), 1-2 in (sets) 4-6 in 110
Peas[13] 40°F 1 in 4-6 in 65
Radishes[13] 40°F 1/2 in 2-3 in 30
Spinach[13] 40°F 1/2 in 4-6 in 40
Turnips[13] 40°F 1/2 in 4-6 in 50
Beets[13] 40°F 3/4-1 in 4-6 in 60
Carrots[13] 40°F 1/4 in 2-3 in 70
Cauliflower[13] 40°F 1/2 in 18 in –
Parsnips[13] 35°F 1/2 in 5-6 in 70
Potatoes[13] 45°F – – 125
Swiss chard[13] 40°F 1 in 7-9 in 60
Snap beans[13] 55°F 1-1 1/2 in 6 in 60
Sweet corn[13] 50°F 1-1 1/2 in 12 x 30 in or 9 x 36 in 60-90
Cucumbers[13] 60°F 1 in 6 in trellised, 24-36 in untrellised 55
Summer squash[13] 60°F 1-1 1/2 in 36-48 in 50
Cantaloupe[13] 60°F 1-1 1/2 in 36-48 in 85
Eggplant[13] 60°F 1/4 in 18-24 in 60
Peppers[13] 60°F 1/4 in 15-18 in 70
Tomatoes[13] 50°F 1/4 in 24 in trellised 65
Winter squash[13] 60°F 1-1 1/2 in 36-48 in 100
Watermelon[13] 60°F 1-1 1/2 in 36-48 in 85

Hardiness zone

Zone 6b means an average coldest winter night of -5°F to 0°F over 1991 to 2020[1]. The zone is based on that winter low, not on summer heat or frost dates[14]. USDA describes the map as the standard gardeners use to judge which perennial plants are most likely to thrive in a place[14]. By land area, 100% of Detroit lies in ZIP code areas rated zone 6b[15].

Zone 6b: average annual extreme minimum temperature -5°F to 0°F (1991 to 2020)[1]. Modeled value at the city center: -2.8°F[1].

Share of the city's land area by ZIP code zone: zone 6b 100%[15].

All towns in zone 6b and what zone 6b means

Zone by ZIP code
ZIP code Zone Coldest night range
48228[15] 6b -5 to 0°F
48219[15] 6b -5 to 0°F
48234[15] 6b -5 to 0°F
48227[15] 6b -5 to 0°F
48209[15] 6b -5 to 0°F
48213[15] 6b -5 to 0°F
48205[15] 6b -5 to 0°F
48207[15] 6b -5 to 0°F
48235[15] 6b -5 to 0°F
48223[15] 6b -5 to 0°F
48224[15] 6b -5 to 0°F
48238[15] 6b -5 to 0°F
48203[15] 6b -5 to 0°F
48221[15] 6b -5 to 0°F
48214[15] 6b -5 to 0°F
48204[15] 6b -5 to 0°F
48210[15] 6b -5 to 0°F
48215[15] 6b -5 to 0°F
48211[15] 6b -5 to 0°F
48212[15] 6b -5 to 0°F
48202[15] 6b -5 to 0°F
48208[15] 6b -5 to 0°F
48206[15] 6b -5 to 0°F
48217[15] 6b -5 to 0°F
48216[15] 6b -5 to 0°F
48201[15] 6b -5 to 0°F
48239[15] 6b -5 to 0°F
48226[15] 6b -5 to 0°F
48236[15] 6b -5 to 0°F
48240[15] 6b -5 to 0°F

Questions people ask

What growing zone is Detroit?
The 2023 USDA map puts Detroit in zone 6b[1]. By land area, 100% of the city lies in ZIP code areas rated zone 6b[15].
When is the last frost in Detroit?
The median last spring frost is April 21 at the Detroit City Airport station[2]. In 1 of 10 years the last frost comes after May 6[2].
When to plant tomatoes in Detroit?
CSU Extension says very tender crops like tomatoes typically go in 2 or more weeks after the average last frost[10]. For Detroit the earliest start is May 5[10].
When is the first frost in Detroit?
The median first fall frost is October 31[3]. In 1 of 10 years the first frost comes before October 17[3].
How long is the growing season in Detroit?
In half of years the growing season is at least 190 days, and in 9 of 10 years it is at least 171 days[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Detroit, Michigan in zone 6b. Zone 6b means an average annual extreme minimum temperature of -5°F to 0°F over 1991 to 2020. The map's modeled value at the city center is minus 2.8°F. USDA zone map 2023 (PRISM, OSU)
  2. Last spring frost (32°F) at this station: in 9 of 10 years the last frost comes after April 7, in half of years after April 21, and in 1 of 10 years after May 6 (NOAA 1991 to 2020 normals). The median last frost date is April 21. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before October 17, in half of years before October 31, and in 9 of 10 years before November 11 (NOAA 1991 to 2020 normals). The median first frost date is October 31. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 171 days in 9 of 10 years, at least 190 days in half of years, and at least 208 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Detroit City Airport weather station (USW00014822), 5 miles from the center of Detroit at 626 feet, using 29 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. Colorado State University Extension's vegetable planting guide (written for Colorado) groups broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips as hardy vegetables, with this rule: as early as 2-4 weeks before the average last... CSU Extension GardenNotes #720
  7. Hard freeze (28°F) at this station: the median last spring date is April 8 and the median first fall date is November 9. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 100% of years from 1991 to 2020, and 28°F or colder in 100% of years. NOAA Climate Normals 1991-2020
  9. Colorado State University Extension's vegetable planting guide (written for Colorado) groups snap beans, sweet corn, cucumbers, summer squash as tender vegetables, with this rule: from seed around the average last spring frost; cucumber and summer squash... CSU Extension GardenNotes #720
  10. Colorado State University Extension's vegetable planting guide (written for Colorado) groups cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon as very tender vegetables, with this rule: typically 2 or more weeks after the average last... CSU Extension GardenNotes #720
  11. Colorado State University Extension's vegetable planting guide (written for Colorado) groups beets, carrots, cauliflower, parsnips, potatoes, Swiss chard as semi-hardy vegetables, with this rule: as early as 0-2 weeks before the average last spring frost.... CSU Extension GardenNotes #720
  12. GardenFacts calculation: earliest planting date plus CSU days to harvest (table on this page), from the station's median last frost. NOAA Climate Normals 1991-2020
  13. CSU Extension vegetable table: soil temperature, depth, spacing, days to harvest (table on this page). CSU Extension GardenNotes #720
  14. USDA hardiness zones are based on the average annual extreme minimum winter temperature (the coldest night of each winter, averaged over 1991 to 2020 for the 2023 map), not on summer heat or frost dates. Each zone spans 10°F and each half zone (a or b)... USDA Plant Hardiness Zone Map
  15. Detroit, Michigan overlaps 34 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 6b. USDA zone map 2023 (PRISM, OSU)

Frost dates are probabilities from 1991 to 2020 weather records at one NOAA station, not a forecast. Any year can be earlier or later. The hardiness zone describes the average coldest winter night, not frost dates or summer heat. Spots inside the city can differ (ZIP table). Planting rules come from Colorado State University Extension's guide, written for Colorado. A local extension office may give dates tuned to the area. Planting and harvest dates marked GardenFacts calculation are simple arithmetic from the facts above, not advice from the source.

Hardiness zone data: USDA Plant Hardiness Zone Map (2023), USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu, accessed October 30, 2026. This is not the official USDA map. Frost data: NOAA NCEI U.S. Climate Normals 1991-2020. Planting rules: Colorado State University Extension.