Harbison Canyon climate

Harbison Canyon Frost Dates and Growing Season

NOAA 1991-2020 normals for El Capitan Dam, 7.4 km from Harbison Canyon, elevation 600 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for El Capitan Dam. 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 March 19 and the first fall freeze around December 8, a growing season of about 270 days.

Median at 36°F
last April 24, first November 19
Median at 32°F
last March 19, first December 8
Median at 28°F
last February 22, first January 1

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 29Jun 14May 29May 5Apr 24Apr 13Mar 31Mar 14Feb 23
32°FJun 1May 3Apr 14Mar 31Mar 19Feb 28Feb 19Jan 29Dec 31
28°FApr 20Mar 29Mar 13Feb 28Feb 22Feb 12Jan 31Jan 14Dec 20
24°FMar 28Feb 28Feb 22Feb 14Feb 4Jan 30Jan 20Jan 11Dec 27
20°F–––––––––
16°F–––––––––

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 16Oct 7Oct 28Nov 9Nov 19Nov 25Nov 30Dec 4Dec 13
32°FOct 25Nov 16Nov 28Dec 1Dec 8Dec 14Dec 21Dec 30Jan 15
28°FNov 26Dec 4Dec 14Dec 26Jan 1Jan 8Jan 22Feb 5Feb 25
24°FDec 6Dec 31Jan 5Jan 11Jan 18Jan 26Feb 3Feb 17Mar 1
20°F–––––––––
16°F–––––––––

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°F274253234214198182167150124
32°F343322303285270252233212184
28°F365365363345333315302279246
24°F365365365365365365354334309
20°F365365365365365365365365365
16°F365365365365365365365365365

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
97% of years
28°F or colder
72% of years
24°F or colder
37% of years
20°F or colder
8% of years
16°F or colder
1% 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
1,396
Cooling degree days, base 65°F
1,572
Growing degree days, base 40°F
9,301
Growing degree days, base 45°F
7,483
Growing degree days, base 50°F
5,704
Growing degree days, base 55°F
4,057
Growing degree days, base 60°F
2,661

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January2705213
February24810196
March21817272
April13744360
May50112527
June21161590
July1334798
August1383848
September3288735
October27171609
November13943357
December2825201

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 7.4 km from Harbison Canyon. 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 USC00042709 (El Capitan Dam). Public domain.