Rocky Ford climate

Rocky Ford Frost Dates and Growing Season

NOAA 1991-2020 normals for Rocky Ford 2 Se, 2.8 km from Rocky Ford, elevation 4170 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rocky Ford 2 Se. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 1 and the first fall freeze around October 8, a growing season of about 159 days.

Median at 36°F
last May 11, first September 30
Median at 32°F
last May 1, first October 8
Median at 28°F
last April 21, first October 16

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 25May 20May 17May 14May 11May 9May 7May 4Apr 30
32°FMay 14May 10May 6May 4May 1Apr 29Apr 27Apr 24Apr 20
28°FMay 3Apr 29Apr 26Apr 23Apr 21Apr 18Apr 15Apr 12Apr 7
24°FApr 22Apr 18Apr 14Apr 10Apr 7Apr 4Apr 1Mar 29Mar 24
20°FApr 10Apr 5Apr 2Mar 31Mar 28Mar 24Mar 20Mar 16Mar 11
16°FApr 1Mar 26Mar 21Mar 17Mar 14Mar 11Mar 8Mar 4Feb 28

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 19Sep 23Sep 26Sep 28Sep 30Oct 2Oct 4Oct 6Oct 10
32°FSep 26Oct 1Oct 3Oct 5Oct 8Oct 10Oct 12Oct 15Oct 19
28°FOct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 21Oct 24Oct 27
24°FOct 13Oct 16Oct 20Oct 23Oct 26Oct 29Oct 31Nov 2Nov 6
20°FOct 21Oct 25Oct 29Nov 1Nov 3Nov 6Nov 8Nov 11Nov 15
16°FOct 27Nov 2Nov 5Nov 8Nov 11Nov 14Nov 17Nov 20Nov 24

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F158151147144141138135131125
32°F176170165162159155152148142
28°F197190185181178175171167160
24°F217211206203200195191187180
20°F239232227223219215211206200
16°F260253248243239234230223216

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
5,165
Cooling degree days, base 65°F
1,107
Growing degree days, base 40°F
5,995
Growing degree days, base 45°F
4,727
Growing degree days, base 50°F
3,609
Growing degree days, base 55°F
2,637
Growing degree days, base 60°F
1,804

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,03801
February82406
March619046
April3594153
May13262403
June10248688
July1363828
August2304767
September56118515
October3538181
November729021
December1,04301

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 2.8 km from Rocky Ford. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00057167 (Rocky Ford 2 Se). Public domain.