USDA Hardiness Zone 6b
Frost Dates for 48228 — Detroit, Michigan
NOAA 1991–2020 normals from Dearborn #2, MI (605 ft), 2 miles east.
Updated
In Detroit, the last spring frost (32°F) is around April 27 in half of years and has passed by May 11 in nine years out of ten. The first fall frost comes around October 25, as early as October 10 one year in ten, leaving a typical freeze-free season of 181 days (NOAA, Dearborn #2, MI).
- Last spring frost
- April 27
- First fall frost
- October 25
- Growing season
- 181 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- December 4
- Last snow
- March 26
- Winters with snow
- 100%
- Snow per year
- 30.8"
median, 1991–2020
median, 1991–2020
24 of 24 observed
NOAA normal
Frost risk by date in Detroit
Half of springs at Dearborn #2, MI see their last 32°F night by April 27; only one in ten is past it by April 12, and one in ten still has one after May 11. Planting tender crops after May 2 leaves a 30% risk of a frost on them, after May 6 20%, and after May 11 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 80% of the 172 Michigan stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 25 in half of years, as early as October 10 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 12 days later, around November 6; in spring the one-in-ten date for 28°F is April 30, 11 days before the 32°F one. The freeze-free season lasts 181 days in a typical year, longer than at 96% of the 172 Michigan stations; it reaches 199 days one year in ten and falls short of 159 one year in ten. On average 125 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 9 days longer, to about May 6, and return around October 13. Severe cold of 16°F or below comes every winter, usually between December 11 and March 13.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 25 | Apr 29 | May 1 | May 4 | May 6 | May 9 | May 12 | May 16 | May 21 |
| 32°F | Apr 12 | Apr 17 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 2 | May 6 | May 11 |
| 28°F | Apr 1 | Apr 5 | Apr 8 | Apr 11 | Apr 15 | Apr 17 | Apr 20 | Apr 25 | Apr 30 |
| 24°F | Mar 18 | Mar 23 | Mar 27 | Mar 31 | Apr 2 | Apr 4 | Apr 7 | Apr 10 | Apr 15 |
| 20°F | Mar 7 | Mar 12 | Mar 16 | Mar 19 | Mar 22 | Mar 25 | Mar 29 | Mar 31 | Apr 4 |
| 16°F | Feb 24 | Mar 3 | Mar 7 | Mar 10 | Mar 13 | Mar 16 | Mar 19 | Mar 23 | Mar 28 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 30 | Oct 3 | Oct 6 | Oct 9 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 27 |
| 32°F | Oct 10 | Oct 16 | Oct 20 | Oct 23 | Oct 25 | Oct 29 | Oct 31 | Nov 3 | Nov 7 |
| 28°F | Oct 24 | Oct 29 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 21 |
| 24°F | Nov 4 | Nov 9 | Nov 12 | Nov 15 | Nov 19 | Nov 22 | Nov 25 | Nov 29 | Dec 3 |
| 20°F | Nov 12 | Nov 19 | Nov 23 | Nov 27 | Dec 1 | Dec 3 | Dec 6 | Dec 11 | Dec 18 |
| 16°F | Nov 24 | Dec 1 | Dec 4 | Dec 7 | Dec 11 | Dec 16 | Dec 20 | Dec 24 | Dec 31 |
Freeze probabilities 1991–2020 at Dearborn #2, MI, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 48228 →Compare Detroit with another place →
Weather by month in Detroit
July is the warmest month at Dearborn #2, MI, averaging 84°F by day and 63°F at night; January is the coldest at 33°F and 19°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 34% of years.
Warmth for growing adds up to 3,018 growing degree days a year (base 50°F), more than at 97% of the 172 Michigan stations. 32% of them (975) have built up by the end of June, and July adds the most, 736.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 33 | 19 | 100% | 28 | 1 |
| Feb | 36 | 20 | 100% | 26 | 1 |
| Mar | 46 | 27 | 100% | 23 | 18 |
| Apr | 59 | 37 | 99% | 8 | 79 |
| May | 70 | 48 | 34% | <1 | 298 |
| Jun | 79 | 59 | 0% | 0 | 579 |
| Jul | 84 | 63 | 0% | 0 | 736 |
| Aug | 82 | 62 | 0% | 0 | 685 |
| Sep | 75 | 55 | 1% | 0 | 447 |
| Oct | 63 | 43 | 71% | 2 | 153 |
| Nov | 49 | 33 | 100% | 15 | 20 |
| Dec | 37 | 25 | 100% | 24 | 2 |
Monthly normals 1991–2020 at Dearborn #2, MI (605 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Dearborn, MI, 3 miles southwest of Detroit, has a last frost 4 days later (May 1), a first frost 10 days earlier (October 15), a season 15 days shorter.
When it snows in Detroit, Michigan
The first measurable snow (0.1 inch or more) in Detroit usually arrives around December 4, and the last of the season around March 26. Those are the middle dates across the winters of 1991–2020 at Dearborn, MI, 2.7 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 32 days after the last snow.
Planting calendar for 48228
| When | What to do |
|---|---|
| February 16 – March 2 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 2 – March 16 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 30 – April 13 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 27 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 2 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 11 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 25 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 48228 is 2 miles from Dearborn #2, MI, which stands at 605 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 17 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 48228 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.