Rifle climate

Rifle Frost Dates and Growing Season

NOAA 1991-2020 normals for Rifle 3ENE, 5.5 km from Rifle, elevation 5469 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rifle 3ENE. 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 23 and the first fall freeze around September 25, a growing season of about 124 days.

Median at 36°F
last June 5, first September 16
Median at 32°F
last May 23, first September 25
Median at 28°F
last May 9, first October 4

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°FJun 19Jun 13Jun 10Jun 7Jun 5Jun 2May 31May 27May 22
32°FJun 6Jun 2May 30May 26May 23May 20May 17May 14May 9
28°FMay 24May 19May 16May 12May 9May 6May 3Apr 30Apr 26
24°FMay 10May 5May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14
20°FApr 28Apr 23Apr 20Apr 16Apr 14Apr 10Apr 7Apr 4Mar 31
16°FApr 17Apr 8Apr 4Apr 1Mar 29Mar 24Mar 20Mar 16Mar 10

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 5Sep 9Sep 12Sep 14Sep 16Sep 18Sep 21Sep 23Sep 26
32°FSep 13Sep 17Sep 20Sep 23Sep 25Sep 27Sep 29Oct 2Oct 6
28°FSep 23Sep 27Sep 29Oct 1Oct 4Oct 6Oct 9Oct 13Oct 17
24°FSep 30Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 23Oct 26
20°FOct 10Oct 15Oct 18Oct 21Oct 24Oct 26Oct 29Nov 2Nov 8
16°FOct 19Oct 24Oct 28Nov 1Nov 3Nov 6Nov 9Nov 13Nov 17

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°F11911410910510299969185
32°F142136132127124120116111105
28°F166159155151147143139134127
24°F188181177173170165161157150
20°F212205200195192189185180173
16°F239232227221217213209204196

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
7,093
Cooling degree days, base 65°F
330
Growing degree days, base 40°F
4,050
Growing degree days, base 45°F
3,013
Growing degree days, base 50°F
2,130
Growing degree days, base 55°F
1,387
Growing degree days, base 60°F
777

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,28500
February1,02100
March82802
April597027
May3415168
June8350417
July6167626
August2396538
September17613295
October560055
November91102
December1,26300

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 5.5 km from Rifle. 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 USC00057033 (Rifle 3ENE). Public domain.