Bruin climate

Bruin Frost Dates and Growing Season

NOAA 1991-2020 normals for Butler 2 Sw, 28.6 km from Bruin, elevation 1000 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Butler 2 Sw. 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 7 and the first fall freeze around October 14, a growing season of about 159 days.

Median at 36°F
last May 19, first October 3
Median at 32°F
last May 7, first October 14
Median at 28°F
last April 26, first October 27

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 1May 29May 25May 22May 19May 16May 11May 7May 1
32°FMay 23May 19May 14May 10May 7May 3Apr 30Apr 27Apr 22
28°FMay 14May 8May 2Apr 29Apr 26Apr 23Apr 19Apr 16Apr 10
24°FApr 28Apr 21Apr 18Apr 14Apr 11Apr 7Apr 4Apr 1Mar 28
20°FApr 12Apr 6Apr 3Apr 1Mar 30Mar 27Mar 23Mar 19Mar 14
16°FApr 1Mar 29Mar 25Mar 21Mar 18Mar 16Mar 12Mar 8Mar 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 21Sep 25Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 15
32°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 24Oct 30
28°FOct 12Oct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 4Nov 9
24°FOct 26Nov 1Nov 2Nov 5Nov 8Nov 10Nov 13Nov 16Nov 21
20°FNov 6Nov 10Nov 13Nov 17Nov 20Nov 23Nov 27Dec 1Dec 6
16°FNov 13Nov 18Nov 22Nov 27Dec 1Dec 4Dec 8Dec 14Dec 21

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°F157150144140136133129125118
32°F179173168163159155151146139
28°F204198192188183179175170162
24°F231223219214210207203198191
20°F258249244238234230225221214
16°F283276269264259254249243235

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
6,457
Cooling degree days, base 65°F
480
Growing degree days, base 40°F
4,635
Growing degree days, base 45°F
3,510
Growing degree days, base 50°F
2,533
Growing degree days, base 55°F
1,695
Growing degree days, base 60°F
1,003

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21502
February1,04002
March905016
April533279
May26126257
June6396484
July14167618
August22138581
September13846363
October4575111
November759016
December1,04904

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 28.6 km from Bruin. 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 USC00361139 (Butler 2 Sw). Public domain.