ZIP 52401 Zone 5b

Iowa · USDA zone 5b, average annual extreme minimum -15°F to -10°F.

Nearest qualified station: CEDAR RAPIDS #1, IA US (USC00131319), 6.3 miles from the Census ZCTA internal point for this ZIP.

Median last 32°F is April 28. Median first 32°F is October 12. The 50% growing-season length is 166 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 14Earlier date. A last 32°F on or after this day is common.
50%April 28Median.
10%May 13Later 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 29Earlier date. A first 32°F on or before this day is uncommon.
50%October 12Median.
90%October 25Later 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%184
50%166
90%144

28°F threshold

10%50%90%
Last, on or afterMay 2April 17April 4
First, on or beforeOctober 8October 22November 1
Season at least205 days186 days166 days

36°F threshold

10%50%90%
Last, on or afterMay 22May 7April 23
First, on or beforeSeptember 19October 2October 14
Season at least166 days147 days128 days

Station CEDAR RAPIDS #1, IA US (USC00131319). Completeness flag S, 30 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 247.8 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Methodology · Iowa cities