Frost Dates for 48219 — Detroit, Michigan

Half of springs at Farmington, MI see their last 32°F night by May 1; only one in ten is past it by April 19, and one in ten still has one after May 16. Planting tender crops after May 8 leaves a 30% risk of a frost on them, after May 11 20%, and after May 16 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 55% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 17 in half of years, as early as October 1 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 10 days later, around October 27; in spring the one-in-ten date for 28°F is May 5, 11 days before the 32°F one. The freeze-free season lasts 165 days in a typical year, longer than at 69% of the 172 Michigan stations; it reaches 183 days one year in ten and falls short of 146 one year in ten. On average 146 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 12 days longer, to about May 13, and return around October 4. Severe cold of 16°F or below comes every winter, usually between November 30 and March 20.

July is the warmest month at Farmington, MI, averaging 83°F by day and 60°F at night; January is the coldest at 30°F and 16°F. A freezing night is all but certain in every month from October 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 54% of years.

Warmth for growing adds up to 2,601 growing degree days a year (base 50°F), more than at 63% of the 172 Michigan stations. 32% of them (833) have built up by the end of June, and July adds the most, 662. Precipitation totals 33.2 inches a year, most in May (3.6") and least in February (1.8"); May to September bring 50% of it.

The nearest other station, Dearborn #2, MI, 7 miles southeast of Detroit, has a last frost 4 days earlier (April 27), a first frost 8 days later (October 25), a season 16 days longer.

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, 7.3 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 36 days after the last snow.

ZIP 48219 is 7 miles from Farmington, MI, which stands at 720 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 21 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 48219 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.