Alamosa climate

Alamosa Frost Dates and Growing Season

NOAA 1991-2020 normals for Alamosa 1E, 1.2 km from Alamosa, elevation 7540 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alamosa 1E. 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 30 and the first fall freeze around September 17, a growing season of about 108 days.

Median at 36°F
last June 14, first September 5
Median at 32°F
last May 30, first September 17
Median at 28°F
last May 16, first September 27

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 30Jun 24Jun 20Jun 17Jun 14Jun 12Jun 10Jun 7Jun 4
32°FJun 13Jun 7Jun 4Jun 2May 30May 28May 25May 22May 17
28°FJun 1May 26May 22May 19May 16May 14May 10May 7May 2
24°FMay 18May 13May 10May 7May 4May 1Apr 30Apr 26Apr 22
20°FMay 8May 4Apr 30Apr 28Apr 24Apr 21Apr 18Apr 15Apr 10
16°FApr 28Apr 21Apr 17Apr 14Apr 10Apr 7Apr 4Apr 1Mar 26

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°FAug 19Aug 27Aug 31Sep 3Sep 5Sep 7Sep 9Sep 12Sep 16
32°FSep 4Sep 10Sep 12Sep 14Sep 17Sep 19Sep 21Sep 24Sep 27
28°FSep 16Sep 20Sep 23Sep 25Sep 27Sep 29Oct 1Oct 3Oct 5
24°FSep 25Sep 28Sep 30Oct 2Oct 4Oct 6Oct 8Oct 10Oct 16
20°FOct 1Oct 4Oct 7Oct 9Oct 12Oct 15Oct 17Oct 20Oct 23
16°FOct 7Oct 13Oct 16Oct 19Oct 21Oct 23Oct 26Oct 30Nov 3

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°F989388848177736860
32°F1261191161121081051019791
28°F149144139135132128124120114
24°F167161158155151148144141135
20°F189183178174170167163158152
16°F213205201197192189184178171

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
8,209
Cooling degree days, base 65°F
74
Growing degree days, base 40°F
3,316
Growing degree days, base 45°F
2,350
Growing degree days, base 50°F
1,533
Growing degree days, base 55°F
861
Growing degree days, base 60°F
360

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,47400
February1,12600
March93201
April677012
May4170111
June14612319
July3443474
August8717395
September2711193
October631028
November1,00400
December1,41200

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 1.2 km from Alamosa. 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 USC00050128 (Alamosa 1E). Public domain.