ZIP 48104 Zone 6a

Michigan · USDA zone 6a, average annual extreme minimum -10°F to -5°F.

Nearest qualified station: ANN ARBOR SE, MI US (USC00200228), 1.9 miles from the Census ZCTA internal point for this ZIP.

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.

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

ProbabilityDateHow to read it
10%September 28Earlier date. A first 32°F on or before this day is uncommon.
50%October 10Median.
90%October 24Later 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 longDays
10%176
50%157
90%138

28°F threshold

10%50%90%
Last, on or afterMay 11April 24April 10
First, on or beforeOctober 7October 23November 6
Season at least199 days180 days160 days

36°F threshold

10%50%90%
Last, on or afterMay 29May 15May 1
First, on or beforeSeptember 18October 1October 12
Season at least157 days137 days117 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.

Methodology · Michigan cities