Sierra County climate

Sierra County Frost Dates and Growing Season

NOAA 1991-2020 normals for Elephant Butte Dam, 1.8 km from Sierra County, elevation 4571 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Elephant Butte 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 13 and the first fall freeze around November 15, a growing season of about 243 days.

Median at 36°F
last March 30, first November 5
Median at 32°F
last March 13, first November 15
Median at 28°F
last March 1, first November 26

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°FApr 18Apr 9Apr 5Apr 2Mar 30Mar 27Mar 23Mar 18Mar 13
32°FApr 2Mar 28Mar 23Mar 18Mar 13Mar 10Mar 7Mar 4Feb 26
28°FMar 21Mar 13Mar 9Mar 5Mar 1Feb 26Feb 20Feb 14Feb 7
24°FMar 9Mar 1Feb 21Feb 15Feb 9Feb 4Jan 31Jan 24Jan 12
20°FFeb 24Feb 10Feb 3Jan 29Jan 22Jan 16Jan 9Jan 3Dec 25
16°FFeb 7Jan 27Jan 17Jan 12Jan 6Dec 31Dec 24Dec 19Dec 12

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 22Oct 27Oct 31Nov 2Nov 5Nov 7Nov 10Nov 13Nov 17
32°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 21Nov 24Nov 28
28°FNov 11Nov 16Nov 20Nov 23Nov 26Nov 29Dec 2Dec 5Dec 11
24°FNov 23Nov 28Dec 3Dec 5Dec 8Dec 12Dec 17Dec 22Dec 30
20°FDec 3Dec 8Dec 14Dec 18Dec 23Dec 30Jan 5Jan 12Jan 24
16°FDec 7Dec 13Dec 18Dec 22Dec 29Jan 3Jan 9Jan 16Jan 31

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°F240231225221218213209204196
32°F265258252248243238232226218
28°F296286280275269264259252244
24°F332322314307300294288279268
20°F365361352345339333326316302
16°F365365365365365365356346336

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
85% of years
16°F or colder
43% 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
2,774
Cooling degree days, base 65°F
2,209
Growing degree days, base 40°F
8,658
Growing degree days, base 45°F
7,028
Growing degree days, base 50°F
5,574
Growing degree days, base 55°F
4,295
Growing degree days, base 60°F
3,177

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January674012
February475046
March3227187
April11151394
May17231679
June0500949
July05571,022
August0494959
September5298743
October9770444
November3922125
December682015

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 1.8 km from Sierra County. 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 USC00292848 (Elephant Butte Dam). Public domain.