Severance climate

Severance Frost Dates and Growing Season

NOAA 1991-2020 normals for Ft Collins 4 E, 15.7 km from Severance, elevation 4920 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ft Collins 4 E. 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 3 and the first fall freeze around October 6, a growing season of about 154 days.

Median at 36°F
last May 14, first September 27
Median at 32°F
last May 3, first October 6
Median at 28°F
last April 23, first October 14

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 26May 22May 18May 16May 14May 12May 9May 7May 3
32°FMay 15May 11May 8May 6May 3May 1Apr 29Apr 26Apr 21
28°FMay 8May 3Apr 30Apr 26Apr 23Apr 20Apr 17Apr 13Apr 8
24°FApr 28Apr 23Apr 19Apr 15Apr 11Apr 8Apr 4Apr 1Mar 28
20°FApr 18Apr 11Apr 6Apr 3Mar 31Mar 28Mar 24Mar 19Mar 12
16°FApr 4Mar 31Mar 25Mar 21Mar 18Mar 14Mar 9Mar 5Feb 27

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 13Sep 18Sep 22Sep 25Sep 27Sep 29Oct 1Oct 4Oct 8
32°FSep 22Sep 27Oct 1Oct 3Oct 6Oct 9Oct 11Oct 14Oct 17
28°FSep 30Oct 5Oct 9Oct 12Oct 14Oct 17Oct 20Oct 23Oct 26
24°FOct 8Oct 14Oct 18Oct 21Oct 24Oct 27Oct 30Nov 2Nov 6
20°FOct 18Oct 23Oct 28Oct 31Nov 3Nov 5Nov 8Nov 12Nov 16
16°FOct 24Oct 31Nov 4Nov 7Nov 11Nov 14Nov 17Nov 21Nov 25

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°F151146142139136132128123118
32°F171164161157154150146142135
28°F192186181177174169165159153
24°F214207202197194189185180172
20°F237230225219215211206200191
16°F260252247242237231226219210

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
6,270
Cooling degree days, base 65°F
584
Growing degree days, base 40°F
4,734
Growing degree days, base 45°F
3,592
Growing degree days, base 50°F
2,614
Growing degree days, base 55°F
1,792
Growing degree days, base 60°F
1,118

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,11600
February93401
March753016
April528063
May27613235
June55106502
July5242702
August14177628
September13946367
October500092
November82809
December1,12200

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 15.7 km from Severance. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00053006 (Ft Collins 4 E). Public domain.