ZIP 80120 Zone 6a

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

Nearest qualified station: MARSTON FLTR PLT, CO US (USC00055402), 3.4 miles from the Census ZCTA internal point for this ZIP.

Median last 32°F is May 2. Median first 32°F is October 11. The 50% growing-season length is 160 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 20Earlier date. A last 32°F on or after this day is common.
50%May 2Median.
10%May 17Later 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 27Earlier date. A first 32°F on or before this day is uncommon.
50%October 11Median.
90%October 23Later 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%181
50%160
90%139

28°F threshold

10%50%90%
Last, on or afterMay 7April 23April 8
First, on or beforeOctober 6October 21November 5
Season at least200 days180 days160 days

36°F threshold

10%50%90%
Last, on or afterMay 29May 12April 30
First, on or beforeSeptember 17October 2October 15
Season at least160 days142 days120 days

Station MARSTON FLTR PLT, CO US (USC00055402). Completeness flag R, 18 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 1709.9 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Methodology · Colorado cities