Grant County climate

Grant County Frost Dates and Growing Season

NOAA 1991-2020 normals for Carson, 9 km from Grant County, elevation 2335 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Carson. 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 19 and the first fall freeze around September 25, a growing season of about 127 days.

Median at 36°F
last May 29, first September 16
Median at 32°F
last May 19, first September 25
Median at 28°F
last May 11, first October 2

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 9Jun 5Jun 2May 31May 29May 26May 24May 21May 17
32°FJun 1May 28May 25May 22May 19May 17May 14May 11May 7
28°FMay 25May 20May 16May 13May 11May 8May 5May 3Apr 29
24°FMay 16May 11May 8May 5May 3Apr 30Apr 27Apr 23Apr 18
20°FMay 8May 3Apr 30Apr 28Apr 24Apr 21Apr 18Apr 14Apr 10
16°FApr 30Apr 25Apr 21Apr 18Apr 15Apr 13Apr 9Apr 5Apr 1

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°FAug 31Sep 5Sep 9Sep 13Sep 16Sep 20Sep 22Sep 24Sep 28
32°FSep 11Sep 17Sep 20Sep 22Sep 25Sep 27Sep 30Oct 3Oct 8
28°FSep 20Sep 24Sep 27Sep 30Oct 2Oct 5Oct 8Oct 12Oct 16
24°FSep 27Oct 1Oct 5Oct 8Oct 11Oct 14Oct 16Oct 20Oct 24
20°FOct 5Oct 9Oct 13Oct 16Oct 19Oct 22Oct 25Oct 29Nov 2
16°FOct 12Oct 17Oct 21Oct 24Oct 28Oct 31Nov 3Nov 6Nov 11

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°F126120116112108105999588
32°F144139135131127123119115108
28°F163156151147143140136131124
24°F181174169164161156152148140
20°F196191185181176172169164157
16°F216208203197193190186180173

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
8,714
Cooling degree days, base 65°F
428
Growing degree days, base 40°F
3,860
Growing degree days, base 45°F
2,920
Growing degree days, base 50°F
2,103
Growing degree days, base 55°F
1,406
Growing degree days, base 60°F
846

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,57300
February1,31201
March1,12406
April727128
May3858161
June11560398
July30176611
August55142553
September23241288
October663154
November1,04304
December1,45700

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 9 km from Grant County. 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 USC00321370 (Carson). Public domain.