ZIP 61701 Zone 6a

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

Nearest qualified station: BLOOMINGTON 5W, IL US (USC00110764), 5 miles from the Census ZCTA internal point for this ZIP.

Median last 32°F is April 21. Median first 32°F is October 20. The 50% growing-season length is 181 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 7Earlier date. A last 32°F on or after this day is common.
50%April 21Median.
10%May 5Later 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%October 9Earlier date. A first 32°F on or before this day is uncommon.
50%October 20Median.
90%November 1Later 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%198
50%181
90%161

28°F threshold

10%50%90%
Last, on or afterApril 23April 9March 26
First, on or beforeOctober 18October 30November 11
Season at least223 days203 days184 days

36°F threshold

10%50%90%
Last, on or afterMay 17May 1April 19
First, on or beforeSeptember 27October 11October 22
Season at least179 days160 days139 days

Station BLOOMINGTON 5W, IL US (USC00110764). Completeness flag R, 12 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 259.7 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Methodology · Illinois cities