Black Diamond climate

Black Diamond Frost Dates and Growing Season

NOAA 1991-2020 normals for Palmer 3 Ese, 11.4 km from Black Diamond, elevation 920 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Palmer 3 Ese. 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 3 and the first fall freeze around November 11, a growing season of about 219 days.

Median at 36°F
last May 1, first October 23
Median at 32°F
last April 3, first November 11
Median at 28°F
last February 28, first December 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°FMay 19May 12May 8May 4May 1Apr 28Apr 23Apr 17Apr 11
32°FMay 2Apr 26Apr 19Apr 11Apr 3Mar 30Mar 24Mar 17Mar 7
28°FApr 2Mar 19Mar 11Mar 4Feb 28Feb 24Feb 18Feb 8Jan 28
24°FFeb 27Feb 21Feb 16Feb 9Feb 1Jan 25Jan 13Jan 3Dec 19
20°FFeb 21Feb 12Feb 2Jan 26Jan 16Jan 5Dec 31Dec 14Dec 6
16°FFeb 18Feb 7Jan 31Jan 19Jan 10Dec 30Dec 19Dec 10Dec 2

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 6Oct 13Oct 16Oct 19Oct 23Oct 26Oct 29Nov 3Nov 9
32°FOct 25Oct 31Nov 4Nov 7Nov 11Nov 15Nov 21Nov 26Dec 3
28°FNov 7Nov 13Nov 20Nov 26Dec 1Dec 5Dec 11Dec 19Jan 1
24°FNov 21Nov 30Dec 6Dec 11Dec 19Dec 31Jan 5Jan 17Feb 1
20°FNov 29Dec 4Dec 9Dec 18Dec 29Jan 6Jan 16Jan 29Feb 10
16°FDec 1Dec 6Dec 11Dec 20Dec 30Jan 13Jan 22Feb 1Feb 16

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°F198190184179174170165159149
32°F253242233226219211205197185
28°F317302291283276268260250238
24°F365355341333325315308299282
20°F365365365365356343334327312
16°F365365365365365365365346332

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
99% of years
24°F or colder
87% of years
20°F or colder
58% of years
16°F or colder
30% 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
5,452
Cooling degree days, base 65°F
155
Growing degree days, base 40°F
4,110
Growing degree days, base 45°F
2,768
Growing degree days, base 50°F
1,737
Growing degree days, base 55°F
969
Growing degree days, base 60°F
448

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January79401
February67304
March660013
April520142
May3456153
June22115247
July8853431
August7459449
September17521297
October431188
November645012
December82601

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 11.4 km from Black Diamond. 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 USC00456295 (Palmer 3 Ese). Public domain.