Detroit, Michigan Frost Dates, Growing Season & Hardiness Zone

When is the last frost in Detroit?

In half of years, the last 32°F night has passed by Apr 27. In 1 year out of 10, one still comes after May 11. The last 36°F night (frost possible on plants) typically comes later, around May 6, and the last 28°F hard freeze earlier, around Apr 15.

Detroit has a long late-frost tail: 14 days separate the typical date (Apr 27) from the safer 1-in-10 date (May 11). If tender plants go out early, be ready to protect them on cold nights.

Cold nights don't end with the last freeze. The typical last 36°F night (frost possible on plants in low spots) comes around May 6, 9 days after the typical last 32°F night. On clear, calm nights, frost can form on leaves while the thermometer still reads above freezing.

Is it too early to plant in Detroit?

Before Apr 27 the odds of another 32°F night are better than even; after May 11 they are about 1 in 10 or less.

Today's risk is computed in your browser from the same NOAA probability table, shown as the range between the two nearest NOAA probability levels.

When is the first frost in Detroit?

The typical first fall freeze (32°F) comes by Oct 25, but 1 year in 10 it shows up as early as Oct 10. Cold 36°F nights (frost possible on plants) typically start around Oct 13, and the first hard freeze (28°F) typically comes around Nov 6.

For fall crops, count back from Oct 25, or from Oct 10 to be safe. Our planting calendar does the math for each crop.

How long is Detroit's growing season?

Detroit's frost-free season (32°F) typically runs 181 days. In about 1 year out of 10, it's shorter than 159 days.

That's enough time for most warm-season vegetables if they go in on time. Long-season crops do best started from transplants.

Each year the station logs an average of 3,018 growing degree days (base 50°F), a measure of the heat available for crop growth.

How does Detroit's season compare?

Nationwide, across the 56 cities with frost dates on this site, the typical frost-free season here outlasts the one in 21 of them and falls short of the one in 34.

Growing degree days (base 50°F)

Annual normal: 3,018 GDD (NOAA flag R, 13 years). Running total by the end of each month (sum of NOAA daily GDD normals, so the year-end total can differ slightly from the annual normal):

What growing zone is Detroit? (USDA 2023)

Detroit is in USDA zone 6b on the 2023 map, which means an average coldest winter night of -5 to 0°F. Most of the city was 6b on the 2012 map, and 10 of 33 city ZIPs found in both tables moved up half a zone.

Zones: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 2026-10-08. Shown as published in the ZIP tables; this page does not show a zone map. Not the official USDA Plant Hardiness Zone Map (official map: planthardiness.ars.usda.gov).

Does the new zone change Detroit's frost dates?

No. Zones describe only how cold the coldest winter night gets on average. They don't tell you when frost starts or stops. The frost dates for Detroit come from NOAA's 1991–2020 frost probabilities, which the 2023 zone map left untouched. Choose winter-hardy perennials by zone, and schedule planting by frost dates.

Why do Detroit frost dates differ between websites?

Some sources list May 2 for Detroit. That's the 30%-risk date: about 3 years in 10 still see a 32°F night after it. We headline the 50% (median) date, Apr 27.

May 11 is the date we call 'safer': it's the 10%-risk date, with a 32°F night after it in only about 1 year in 10.

May 6 is the typical (50%) date for a 36°F night (frost possible on plants), not a 32°F freeze. Any site that draws the line at 36°F will show later dates.

The choice of weather station matters too. The 9 stations within 25 miles of the city center that pass our quality rules give typical (50%) last 32°F frost dates from Apr 20 to May 1; see the table below.

Which weather station is this based on?

Station

Dearborn #2 (NOAA USC00202016, COOP)

Distance

4.4 mi SW of the city center

Elevation

605 ft; city center 639 ft (USGS), difference −34 ft

Record

NOAA completeness flag R, 14 of 30 years (1991–2020)

Confidence

Medium (rule)

Confidence: Medium. The station passes our quality rules but isn't an ideal match: 4.4 mi away, −34 ft elevation difference (NOAA flag R, 14 of 30 years).

Note: NOAA rates this station's frost statistics 'R' (representative). That means they use 14 of the 30 years in 1991–2020, with missing months filled in from surrounding stations. For comparison, the nearest station with a full 'S' (standard) record, Detroit City Airport (5.0 mi away), has a typical last frost of Apr 21.

Detroit planting dates at a glance

Balanced dates use the 30%-risk last-frost date as the anchor. The Detroit planting calendar has typical and safe dates, fall planting and a month-by-month list for 26 vegetables.

When to plant tomatoes in Detroit · Fall planting dates for Detroit

Frost dates near Detroit

All Michigan cities

Frequently asked questions

What is the average last frost date in Detroit?

The typical (median, 50%) last 32°F night in Detroit is Apr 27, based on NOAA 1991–2020 normals at Dearborn #2. For a safer target, use May 11; after that, only about 1 year in 10 still has a freeze.

When is the first frost in Detroit?

The first 32°F night typically arrives by Oct 25. About 1 year in 10, it comes as early as Oct 10. A 36°F night (frost possible on plants) typically shows up around Oct 13.

What growing zone is Detroit, Michigan?

Detroit is in USDA hardiness zone 6b on the 2023 map. Most of the city was already 6b on the 2012 map, though 10 of 33 city ZIPs changed zone.

Is it too early to plant in Detroit?

If it's before Apr 27, it's too early for frost-tender plants: another 32°F night is more likely than not. From Apr 27 to May 11, the risk falls from 50% to 10%. Cool-season crops such as peas and lettuce can be planted weeks earlier (see the planting calendar).

What temperature is a killing frost?

A light frost is enough to kill tender crops such as tomatoes. CSU Extension describes 28–32°F as a light frost and anything below 28°F as a heavy frost. We report NOAA odds at three thresholds: 36°F (frost possible on plants), 32°F (freeze, our headline) and 28°F (hard freeze).

Is first frost the same as first freeze?

Not quite. A freeze is when the air reaches 32°F. Frost is ice that forms on surfaces, and on calm, clear nights it can form with the air a few degrees above freezing. So in Detroit, the first 36°F night (frost possible on plants) typically comes around Oct 13, before the first 32°F night (Oct 25).

Download & sources

• Add Detroit frost & planting dates to your calendar (.ics, 2027)
• Printable planting calendar (PDF)
• How these numbers are calculated

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal and daily normals, station USC00202016); USDA Plant Hardiness Zone ZIP tables 2023 and 2012 by the PRISM Group, Oregon State University; Census 2020 ZIP/place relationship file; USGS elevation. Long-term odds, not a forecast. Figures and sentences are generated from these data by fixed rules; see the methodology. Last updated 2026-10-08.