Frost dates / Michigan / Ann Arbor

Frost dates in Ann Arbor, MI

The station on this page is ANN ARBOR SE, MI US (USC00200228), 3.1 miles from the city point. Population in the Census 2024 estimate is 122,925.

Zone 6aUSDA average annual extreme minimum -10°F to -5°F, from ZIP 48104 (1.2 miles from the city point used on this page).

Median last 32°F is May 5. Median first 32°F is October 10. The 50% growing-season length is 157 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

Probability	Date	How to read it
90%	April 21	Earlier date. A last 32°F on or after this day is common.
50%	May 5	Median.
10%	May 20	Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

Probability	Date	How to read it
10%	September 28	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 10	Median.
90%	October 24	Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this long	Days
10%	176
50%	157
90%	138

28°F threshold

	10%	50%	90%
Last, on or after	May 11	April 24	April 10
First, on or before	October 7	October 23	November 6
Season at least	199 days	180 days	160 days

36°F threshold

	10%	50%	90%
Last, on or after	May 29	May 15	May 1
First, on or before	September 18	October 1	October 12
Season at least	157 days	137 days	117 days

Station ANN ARBOR SE, MI US (USC00200228). Completeness flag R, 17 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 253.6 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

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Ann Arbor, MI

Zone 6aAverage annual extreme minimum -10°F to -5°F

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Michigan. Nearest qualified station: ANN ARBOR SE, MI US (USC00200228), 3.1 miles. Median last 32°F May 5. Median first 32°F October 10. The 50% growing-season length is 157 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 20	May 5	April 21
First 32°F on or before	September 28	October 10	October 24

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

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Planting calendar

Frost dates for Michigan are above. Planting windows appear for states with a cited extension guide. The fall and seed tools use the numbers you enter and the station dates.

Date checks use your device’s calendar and appear after the page loads.