Farmington climate

Farmington Frost Dates and Growing Season

NOAA 1991-2020 normals for Chalk Hill 2 Ene, 5 km from Farmington, elevation 1980 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chalk Hill 2 Ene. 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 October 1, a growing season of about 135 days.

Median at 36°F
last May 31, first September 21
Median at 32°F
last May 19, first October 1
Median at 28°F
last May 5, first October 10

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 13Jun 7Jun 4Jun 2May 31May 27May 24May 20May 14
32°FJun 2May 29May 25May 22May 19May 15May 10May 6Apr 30
28°FMay 22May 18May 13May 9May 5Apr 30Apr 28Apr 24Apr 20
24°FMay 12May 4Apr 30Apr 26Apr 22Apr 19Apr 16Apr 11Apr 4
20°FApr 27Apr 20Apr 16Apr 11Apr 7Apr 4Apr 1Mar 28Mar 22
16°FApr 13Apr 7Apr 3Apr 1Mar 29Mar 26Mar 22Mar 18Mar 13

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 7Sep 12Sep 15Sep 18Sep 21Sep 24Sep 27Sep 29Oct 3
32°FSep 18Sep 22Sep 25Sep 29Oct 1Oct 4Oct 6Oct 9Oct 13
28°FSep 27Oct 1Oct 5Oct 8Oct 10Oct 13Oct 16Oct 20Oct 24
24°FOct 7Oct 12Oct 16Oct 19Oct 22Oct 25Oct 29Nov 1Nov 5
20°FOct 18Oct 25Oct 29Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17
16°FNov 1Nov 3Nov 6Nov 10Nov 13Nov 17Nov 21Nov 25Dec 2

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°F1331261211171131091059992
32°F157149144139135130126121114
28°F180173167162157153148142135
24°F206199192188182177172167158
20°F230222217212208204200194185
16°F252245240234229225221215208

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
6,822
Cooling degree days, base 65°F
253
Growing degree days, base 40°F
4,183
Growing degree days, base 45°F
3,083
Growing degree days, base 50°F
2,131
Growing degree days, base 55°F
1,327
Growing degree days, base 60°F
686

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,24302
February1,05302
March915016
April540181
May28212227
June9750405
July36100529
August5271484
September19519287
October510184
November800014
December1,10202

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 5 km from Farmington. 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 USC00361350 (Chalk Hill 2 Ene). Public domain.