Portales climate

Portales Frost Dates and Growing Season

NOAA 1991-2020 normals for Portales, 2.1 km from Portales, elevation 4010 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Portales. 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 April 15 and the first fall freeze around October 26, a growing season of about 193 days.

Median at 36°F
last April 25, first October 17
Median at 32°F
last April 15, first October 26
Median at 28°F
last April 2, first November 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°FMay 6May 2Apr 30Apr 27Apr 25Apr 23Apr 20Apr 17Apr 11
32°FApr 30Apr 25Apr 21Apr 18Apr 15Apr 12Apr 8Apr 4Mar 30
28°FApr 21Apr 14Apr 10Apr 6Apr 2Mar 31Mar 27Mar 22Mar 15
24°FApr 8Apr 2Mar 29Mar 24Mar 18Mar 15Mar 11Mar 7Mar 2
20°FMar 24Mar 16Mar 12Mar 8Mar 5Mar 2Feb 27Feb 22Feb 15
16°FMar 9Mar 4Feb 28Feb 24Feb 19Feb 14Feb 9Feb 1Jan 21

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

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°F190185181177174170166162156
32°F212205201196193189185181173
28°F236228223219215211205200193
24°F260254248243238233227221214
20°F286277271266261257252246238
16°F320308300294288281276268258

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
3,434
Cooling degree days, base 65°F
1,672
Growing degree days, base 40°F
7,643
Growing degree days, base 45°F
6,116
Growing degree days, base 50°F
4,755
Growing degree days, base 55°F
3,565
Growing degree days, base 60°F
2,540

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January767011
February570033
March4082132
April18326307
May43158581
June1379828
July0459924
August0406871
September18207640
October17734339
November500179
December766011

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 2.1 km from Portales. 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 USC00297008 (Portales). Public domain.