Saint David climate

Saint David Frost Dates and Growing Season

NOAA 1991-2020 normals for Benson 6SE, 3.6 km from Saint David, elevation 3690 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Benson 6SE. 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 12 and the first fall freeze around November 1, a growing season of about 202 days.

Median at 36°F
last April 26, first October 24
Median at 32°F
last April 12, first November 1
Median at 28°F
last March 23, first November 11

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 10May 4May 1Apr 29Apr 26Apr 24Apr 21Apr 16Apr 12
32°FApr 29Apr 23Apr 19Apr 15Apr 12Apr 9Apr 5Apr 1Mar 26
28°FApr 13Apr 7Apr 1Mar 29Mar 23Mar 17Mar 13Mar 8Mar 2
24°FMar 23Mar 15Mar 9Mar 6Mar 2Feb 26Feb 21Feb 15Feb 6
20°FMar 7Feb 28Feb 20Feb 14Feb 10Feb 5Feb 1Jan 25Jan 12
16°FFeb 21Feb 9Feb 4Jan 30Jan 22Jan 13Jan 6Dec 30Dec 16

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 12Oct 17Oct 19Oct 21Oct 24Oct 26Oct 29Nov 1Nov 5
32°FOct 18Oct 22Oct 26Oct 30Nov 1Nov 3Nov 7Nov 11Nov 15
28°FOct 27Nov 1Nov 5Nov 8Nov 11Nov 14Nov 18Nov 20Nov 26
24°FNov 6Nov 11Nov 15Nov 18Nov 21Nov 24Nov 28Dec 2Dec 7
20°FNov 16Nov 21Nov 26Nov 29Dec 3Dec 6Dec 10Dec 18Dec 29
16°FNov 27Dec 3Dec 8Dec 13Dec 19Dec 26Jan 3Jan 15Jan 30

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°F198191187183180176172167162
32°F224217211206202198194188181
28°F259250244237232226220213204
24°F290281275268262257251245235
20°F330319309301294288282274265
16°F365362349340334329322310297

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
85% 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
2,561
Cooling degree days, base 65°F
1,952
Growing degree days, base 40°F
8,564
Growing degree days, base 45°F
6,865
Growing degree days, base 50°F
5,335
Growing degree days, base 55°F
4,020
Growing degree days, base 60°F
2,900

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January592020
February447055
March3172180
April14430342
May29159595
June1401850
July0518983
August0465930
September2303751
October8272457
November3492149
December600024

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 3.6 km from Saint David. 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 USC00020683 (Benson 6SE). Public domain.