Alpine climate

Alpine Frost Dates and Growing Season

NOAA 1991-2020 normals for Alpine, 1.9 km from Alpine, elevation 4450 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alpine. 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 2 and the first fall freeze around November 3, a growing season of about 216 days.

Median at 36°F
last April 14, first October 25
Median at 32°F
last April 2, first November 3
Median at 28°F
last March 14, first November 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°FApr 30Apr 24Apr 20Apr 16Apr 14Apr 11Apr 7Apr 3Mar 29
32°FApr 20Apr 13Apr 9Apr 5Apr 2Mar 29Mar 24Mar 17Mar 11
28°FApr 6Mar 31Mar 24Mar 18Mar 14Mar 9Mar 5Feb 28Feb 21
24°FMar 21Mar 13Mar 8Mar 2Feb 27Feb 23Feb 18Feb 12Feb 3
20°FMar 8Feb 28Feb 23Feb 18Feb 12Feb 5Jan 31Jan 24Jan 9
16°FFeb 27Feb 17Feb 8Feb 2Jan 28Jan 21Jan 10Dec 31Dec 19

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 10Oct 16Oct 19Oct 22Oct 25Oct 28Oct 31Nov 3Nov 8
32°FOct 19Oct 24Oct 28Nov 1Nov 3Nov 5Nov 10Nov 14Nov 19
28°FOct 30Nov 3Nov 7Nov 11Nov 14Nov 17Nov 20Nov 24Dec 1
24°FNov 8Nov 13Nov 17Nov 21Nov 25Nov 29Dec 3Dec 7Dec 13
20°FNov 19Nov 26Dec 1Dec 5Dec 9Dec 14Dec 20Dec 28Jan 8
16°FNov 30Dec 7Dec 12Dec 20Dec 26Jan 2Jan 10Jan 21Feb 1

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°F213206200195192188183177169
32°F239232226221216211206199192
28°F267257252246241236231223214
24°F300289282276271264259253242
20°F339326317310301295288279268
16°F365365356346336328319309297

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
98% of years
16°F or colder
82% 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
2,467
Cooling degree days, base 65°F
1,688
Growing degree days, base 40°F
8,460
Growing degree days, base 45°F
6,790
Growing degree days, base 50°F
5,247
Growing degree days, base 55°F
3,873
Growing degree days, base 60°F
2,681

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January583053
February426194
March29111223
April10966413
May25220661
June0383832
July0391856
August0352817
September16196631
October10664432
November3425174
December567062

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 1.9 km from Alpine. 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 USC00410174 (Alpine). Public domain.