Hawthorne climate

Hawthorne Frost Dates and Growing Season

NOAA 1991-2020 normals for Hawthorne, 1.1 km from Hawthorne, elevation 4400 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hawthorne. 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 22 and the first fall freeze around October 25, a growing season of about 185 days.

Median at 36°F
last May 5, first October 15
Median at 32°F
last April 22, first October 25
Median at 28°F
last April 5, first November 5

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 29May 21May 14May 9May 5May 1Apr 28Apr 25Apr 20
32°FMay 11May 3Apr 29Apr 25Apr 22Apr 19Apr 16Apr 11Apr 6
28°FApr 26Apr 18Apr 13Apr 9Apr 5Apr 1Mar 27Mar 19Mar 10
24°FApr 6Mar 30Mar 23Mar 16Mar 11Mar 6Mar 2Feb 25Feb 19
20°FMar 13Mar 5Mar 1Feb 25Feb 19Feb 14Feb 8Feb 1Jan 22
16°FFeb 22Feb 14Feb 8Feb 2Jan 29Jan 22Jan 13Jan 5Dec 29

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 4Oct 7Oct 10Oct 13Oct 15Oct 17Oct 21Oct 24Oct 30
32°FOct 12Oct 16Oct 19Oct 23Oct 25Oct 29Nov 1Nov 5Nov 8
28°FOct 20Oct 25Oct 30Nov 2Nov 5Nov 8Nov 12Nov 15Nov 20
24°FNov 1Nov 6Nov 11Nov 14Nov 17Nov 20Nov 23Nov 27Dec 1
20°FNov 11Nov 17Nov 22Nov 25Nov 29Dec 2Dec 6Dec 11Dec 20
16°FNov 22Nov 29Dec 3Dec 7Dec 11Dec 15Dec 22Dec 29Jan 10

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°F184175170165160156152145136
32°F205200195189185180175168161
28°F239230222215210205200195185
24°F276266259252247241234226217
20°F315303294288282275268261249
16°F353341334326320313306298286

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
97% 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
4,385
Cooling degree days, base 65°F
1,297
Growing degree days, base 40°F
6,471
Growing degree days, base 45°F
5,077
Growing degree days, base 50°F
3,871
Growing degree days, base 55°F
2,849
Growing degree days, base 60°F
2,000

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January86801
February664013
March513069
April3545151
May14666390
June31224644
July1447911
August1382846
September36159574
October27315234
November615035
December88303

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 1.1 km from Hawthorne. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00263512 (Hawthorne). Public domain.