Boron climate

Boron Frost Dates and Growing Season

NOAA 1991-2020 normals for Randsburg, 41.2 km from Boron, elevation 3570 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Randsburg. 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 November 25, a growing season of about 251 days.

Median at 36°F
last April 9, first November 12
Median at 32°F
last March 19, first November 25
Median at 28°F
last February 20, first December 8

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 4Apr 25Apr 18Apr 14Apr 9Apr 5Mar 31Mar 25Mar 16
32°FApr 13Apr 5Mar 31Mar 24Mar 19Mar 12Mar 6Feb 28Feb 20
28°FMar 29Mar 16Mar 7Feb 27Feb 20Feb 12Feb 4Jan 27Jan 12
24°FFeb 27Feb 16Feb 5Jan 29Jan 21Jan 14Jan 6Dec 31Dec 18
20°FJan 27Jan 21Jan 15Jan 12Jan 7Jan 2Dec 31Dec 23Dec 14
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°FOct 24Oct 31Nov 5Nov 9Nov 12Nov 16Nov 19Nov 23Nov 30
32°FNov 5Nov 12Nov 16Nov 20Nov 25Nov 29Dec 3Dec 6Dec 13
28°FNov 18Nov 27Dec 1Dec 5Dec 8Dec 12Dec 16Dec 22Dec 29
24°FNov 29Dec 6Dec 12Dec 18Dec 24Dec 30Jan 4Jan 14Jan 28
20°FDec 9Dec 18Dec 27Dec 31Jan 2Jan 7Jan 13Jan 19Jan 24
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°F245235228221216209203196186
32°F285275265258251245238230219
28°F333320309300291282274265250
24°F365363355347340333324314301
20°F365365365365365365365359346
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
100% of years
28°F or colder
99% of years
24°F or colder
81% of years
20°F or colder
27% of years
16°F or colder
6% 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
2,581
Cooling degree days, base 65°F
2,321
Growing degree days, base 40°F
8,907
Growing degree days, base 45°F
7,218
Growing degree days, base 50°F
5,700
Growing degree days, base 55°F
4,381
Growing degree days, base 60°F
3,264

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January570035
February440071
March3325179
April17240328
May57184593
June6414858
July06111,076
August05831,048
September7365809
October78112501
November3247177
December595028

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 41.2 km from Boron. 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 USC00047253 (Randsburg). Public domain.