Alamo climate

Alamo Frost Dates and Growing Season

NOAA 1991-2020 normals for Pietown 19NE, 35.5 km from Alamo, elevation 7961 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Pietown 19NE. 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 12 and the first fall freeze around October 9, a growing season of about 149 days.

Median at 36°F
last May 26, first October 1
Median at 32°F
last May 12, first October 9
Median at 28°F
last April 30, first October 19

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 10Jun 4Jun 1May 30May 26May 23May 20May 16May 10
32°FMay 31May 24May 19May 15May 12May 8May 5May 1Apr 27
28°FMay 16May 10May 6May 2Apr 30Apr 27Apr 24Apr 20Apr 16
24°FMay 5Apr 30Apr 26Apr 22Apr 19Apr 15Apr 12Apr 7Apr 1
20°FApr 26Apr 17Apr 13Apr 8Apr 5Apr 1Mar 28Mar 22Mar 16
16°FApr 11Apr 2Mar 27Mar 21Mar 16Mar 10Mar 6Mar 2Feb 23

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 18Sep 23Sep 26Sep 28Oct 1Oct 3Oct 6Oct 9Oct 13
32°FSep 27Oct 1Oct 4Oct 6Oct 9Oct 12Oct 16Oct 18Oct 23
28°FOct 5Oct 10Oct 14Oct 17Oct 19Oct 24Oct 26Oct 29Nov 2
24°FOct 16Oct 20Oct 24Oct 27Oct 30Nov 1Nov 5Nov 10Nov 15
20°FOct 24Oct 30Nov 2Nov 5Nov 9Nov 13Nov 16Nov 19Nov 24
16°FNov 1Nov 8Nov 13Nov 16Nov 20Nov 22Nov 25Nov 29Dec 5

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°F147140135131126123118112105
32°F170163158153149144140134126
28°F190184178174170166161155149
24°F213207201196192187182176169
20°F239230225219213209204198189
16°F272264257251245239232225212

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
5,907
Cooling degree days, base 65°F
299
Growing degree days, base 40°F
4,458
Growing degree days, base 45°F
3,287
Growing degree days, base 50°F
2,286
Growing degree days, base 55°F
1,448
Growing degree days, base 60°F
775

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04200
February84801
March735010
April507059
May26611236
June4993496
July17114563
August3465496
September14614321
October447097
November77108
December1,04600

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 35.5 km from Alamo. 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 USC00296812 (Pietown 19NE). Public domain.