Costilla County climate

Costilla County Frost Dates and Growing Season

NOAA 1991-2020 normals for San Luis 1 S, 9.2 km from Costilla County, elevation 7943 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for San Luis 1 S. 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 31 and the first fall freeze around September 23, a growing season of about 115 days.

Median at 36°F
last June 13, first September 14
Median at 32°F
last May 31, first September 23
Median at 28°F
last May 13, first September 30

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 28Jun 23Jun 19Jun 16Jun 13Jun 9Jun 7Jun 4May 31
32°FJun 14Jun 9Jun 5Jun 3May 31May 28May 24May 19May 14
28°FJun 2May 26May 21May 17May 13May 10May 6May 2Apr 29
24°FMay 17May 11May 7May 2Apr 30Apr 28Apr 24Apr 20Apr 14
20°FMay 4Apr 29Apr 25Apr 21Apr 18Apr 14Apr 8Apr 3Mar 25
16°FApr 23Apr 17Apr 11Apr 6Apr 2Mar 29Mar 21Mar 13Mar 7

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 3Sep 7Sep 9Sep 12Sep 14Sep 17Sep 19Sep 23Sep 26
32°FSep 10Sep 14Sep 17Sep 20Sep 23Sep 25Sep 27Oct 1Oct 5
28°FSep 17Sep 22Sep 25Sep 28Sep 30Oct 3Oct 6Oct 9Oct 14
24°FSep 25Sep 30Oct 3Oct 6Oct 10Oct 13Oct 16Oct 19Oct 25
20°FOct 4Oct 9Oct 14Oct 17Oct 20Oct 23Oct 26Oct 31Nov 5
16°FOct 15Oct 20Oct 23Oct 26Oct 29Nov 1Nov 4Nov 8Nov 12

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°F10910398949187837973
32°F13512812311911511010610092
28°F160153148143139135130125116
24°F183176170165161156152146139
20°F211200193188183179174168161
16°F237228220214209203197190181

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
7,719
Cooling degree days, base 65°F
75
Growing degree days, base 40°F
3,390
Growing degree days, base 45°F
2,380
Growing degree days, base 50°F
1,542
Growing degree days, base 55°F
874
Growing degree days, base 60°F
366

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,34400
February1,07200
March85602
April671011
May428199
June15111314
July4143466
August7019414
September2561209
October601025
November95002
December1,27900

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 9.2 km from Costilla County. 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 USC00057430 (San Luis 1 S). Public domain.