Napi Headquarters climate

Napi Headquarters Frost Dates and Growing Season

NOAA 1991-2020 normals for Farmington Ag Sci Cnt, 9.1 km from Napi Headquarters, elevation 5625 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Farmington Ag Sci Cnt. 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 29 and the first fall freeze around October 15, a growing season of about 167 days.

Median at 36°F
last May 12, first October 7
Median at 32°F
last April 29, first October 15
Median at 28°F
last April 17, first October 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°FMay 29May 23May 19May 15May 12May 9May 5May 2Apr 28
32°FMay 13May 8May 4May 1Apr 29Apr 27Apr 24Apr 20Apr 15
28°FMay 2Apr 27Apr 24Apr 20Apr 17Apr 13Apr 9Apr 5Mar 31
24°FApr 20Apr 13Apr 8Apr 4Apr 1Mar 29Mar 23Mar 18Mar 12
20°FApr 3Mar 27Mar 20Mar 16Mar 11Mar 8Mar 4Feb 28Feb 21
16°FMar 12Mar 8Mar 4Feb 28Feb 24Feb 19Feb 15Feb 10Feb 2

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 24Sep 28Oct 2Oct 4Oct 7Oct 10Oct 12Oct 16Oct 20
32°FOct 1Oct 6Oct 9Oct 12Oct 15Oct 18Oct 21Oct 24Oct 29
28°FOct 11Oct 16Oct 19Oct 23Oct 26Oct 29Nov 1Nov 4Nov 10
24°FOct 21Oct 26Oct 30Nov 2Nov 5Nov 8Nov 11Nov 14Nov 19
20°FOct 30Nov 5Nov 8Nov 12Nov 15Nov 17Nov 20Nov 23Nov 28
16°FNov 8Nov 14Nov 18Nov 20Nov 23Nov 26Nov 29Dec 3Dec 9

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°F165159154150146143139133127
32°F186180174171167163159154147
28°F213205198194190186182176170
24°F240231227222217212206201192
20°F269261255250245240235229220
16°F301290284278273268263257248

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
5,321
Cooling degree days, base 65°F
911
Growing degree days, base 40°F
5,585
Growing degree days, base 45°F
4,352
Growing degree days, base 50°F
3,275
Growing degree days, base 55°F
2,346
Growing degree days, base 60°F
1,559

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06800
February80501
March646024
April4221110
May18031330
June21186615
July1334798
August2265728
September6292482
October3513171
November719016
December1,04600

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 9.1 km from Napi Headquarters. 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 USC00293142 (Farmington Ag Sci Cnt). Public domain.