Duncan Falls climate

Duncan Falls Frost Dates and Growing Season

NOAA 1991-2020 normals for Philo 3 Sw, 3.8 km from Duncan Falls, elevation 1020 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Philo 3 Sw. 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 19 and the first fall freeze around October 25, a growing season of about 189 days.

Median at 36°F
last May 1, first October 13
Median at 32°F
last April 19, first October 25
Median at 28°F
last April 4, first November 5

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 19May 13May 9May 5May 1Apr 28Apr 24Apr 20Apr 15
32°FMay 9Apr 30Apr 27Apr 22Apr 19Apr 15Apr 11Apr 7Apr 2
28°FApr 21Apr 15Apr 10Apr 7Apr 4Apr 2Mar 31Mar 26Mar 21
24°FApr 8Apr 3Mar 31Mar 29Mar 26Mar 22Mar 19Mar 15Mar 10
20°FMar 30Mar 25Mar 21Mar 18Mar 15Mar 12Mar 8Mar 4Feb 26
16°FMar 21Mar 16Mar 12Mar 9Mar 5Mar 2Feb 27Feb 22Feb 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 28Oct 3Oct 7Oct 10Oct 13Oct 15Oct 18Oct 22Oct 27
32°FOct 9Oct 15Oct 19Oct 22Oct 25Oct 28Oct 31Nov 2Nov 7
28°FOct 24Oct 30Nov 1Nov 3Nov 5Nov 8Nov 11Nov 15Nov 21
24°FNov 3Nov 7Nov 11Nov 13Nov 17Nov 20Nov 24Nov 30Dec 5
20°FNov 11Nov 17Nov 22Nov 26Dec 1Dec 4Dec 8Dec 13Dec 21
16°FNov 23Nov 29Dec 5Dec 9Dec 13Dec 18Dec 23Dec 28Jan 3

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°F185177172168163159154148140
32°F211203198193189184178172162
28°F238231225220217212207201195
24°F264255250244239235230225216
20°F288280272267262257252246237
16°F309300294289284279273267258

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
5,033
Cooling degree days, base 65°F
972
Growing degree days, base 40°F
6,008
Growing degree days, base 45°F
4,721
Growing degree days, base 50°F
3,569
Growing degree days, base 55°F
2,555
Growing degree days, base 60°F
1,686

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06108
February868010
March694569
April34025205
May14083413
June26186611
July2286749
August6251710
September68114498
October30621222
November605163
December916013

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 3.8 km from Duncan Falls. 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 USC00336600 (Philo 3 Sw). Public domain.