Highland climate

Highland Frost Dates and Growing Season

NOAA 1991-2020 normals for Alpine, 4.7 km from Highland, elevation 5100 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 May 3 and the first fall freeze around October 12, a growing season of about 159 days.

Median at 36°F
last May 20, first October 1
Median at 32°F
last May 3, first October 12
Median at 28°F
last April 16, first October 24

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 3May 29May 24May 20May 17May 13May 9May 4
32°FMay 26May 17May 12May 7May 3Apr 30Apr 28Apr 23Apr 18
28°FMay 5Apr 28Apr 23Apr 20Apr 16Apr 13Apr 8Apr 4Mar 29
24°FApr 17Apr 10Apr 6Apr 2Mar 30Mar 26Mar 20Mar 15Mar 8
20°FApr 1Mar 26Mar 19Mar 14Mar 10Mar 6Mar 3Feb 27Feb 21
16°FMar 13Mar 6Mar 2Feb 27Feb 23Feb 19Feb 15Feb 10Feb 3

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 10Oct 15
32°FSep 29Oct 2Oct 5Oct 9Oct 12Oct 15Oct 18Oct 22Oct 26
28°FOct 8Oct 13Oct 17Oct 20Oct 24Oct 27Oct 31Nov 3Nov 8
24°FOct 19Oct 25Oct 30Nov 2Nov 5Nov 8Nov 11Nov 15Nov 20
20°FOct 29Nov 4Nov 8Nov 12Nov 16Nov 19Nov 22Nov 26Dec 1
16°FNov 8Nov 14Nov 19Nov 22Nov 26Nov 29Dec 2Dec 5Dec 11

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°F154147141136131126121116107
32°F183175169164159154150145137
28°F214206200195190185179173165
24°F244235229224219214210204197
20°F275265258253248243237230221
16°F303293286280276270265258250

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
5,776
Cooling degree days, base 65°F
722
Growing degree days, base 40°F
5,084
Growing degree days, base 45°F
3,893
Growing degree days, base 50°F
2,867
Growing degree days, base 55°F
2,001
Growing degree days, base 60°F
1,292

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,08200
February85501
March679024
April485178
May25818250
June65119506
July3281744
August6236696
September10164418
October4073134
November756016
December1,07800

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 4.7 km from Highland. 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 USC00420061 (Alpine). Public domain.