Armstrong County climate

Armstrong County Frost Dates and Growing Season

NOAA 1991-2020 normals for Vigo Park, 37.1 km from Armstrong County, elevation 3400 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Vigo Park. 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 22, a growing season of about 185 days.

Median at 36°F
last April 29, first October 13
Median at 32°F
last April 19, first October 22
Median at 28°F
last April 8, first October 31

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 9May 6May 3May 1Apr 29Apr 27Apr 23Apr 20Apr 16
32°FMay 1Apr 27Apr 24Apr 21Apr 19Apr 16Apr 13Apr 9Apr 5
28°FApr 24Apr 20Apr 15Apr 12Apr 8Apr 5Apr 2Mar 31Mar 24
24°FApr 16Apr 9Apr 5Apr 2Mar 31Mar 24Mar 20Mar 14Mar 8
20°FApr 4Mar 31Mar 24Mar 18Mar 14Mar 10Mar 6Mar 2Feb 25
16°FMar 22Mar 15Mar 10Mar 5Mar 2Feb 25Feb 21Feb 17Feb 11

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 30Oct 5Oct 8Oct 11Oct 13Oct 16Oct 18Oct 20Oct 24
32°FOct 9Oct 15Oct 17Oct 20Oct 22Oct 24Oct 27Oct 29Nov 2
28°FOct 19Oct 22Oct 26Oct 28Oct 31Nov 2Nov 5Nov 8Nov 13
24°FOct 28Nov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 19Nov 23
20°FNov 3Nov 9Nov 13Nov 16Nov 20Nov 23Nov 25Nov 29Dec 4
16°FNov 12Nov 18Nov 23Nov 26Nov 30Dec 3Dec 6Dec 11Dec 18

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°F182176173170166163160155150
32°F203197193189185181177173166
28°F224219214209205201196191183
24°F248240234230225221216210202
20°F275264258253248243238232223
16°F303292286279274269263256245

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
4,152
Cooling degree days, base 65°F
1,437
Growing degree days, base 40°F
6,953
Growing degree days, base 45°F
5,532
Growing degree days, base 50°F
4,269
Growing degree days, base 55°F
3,175
Growing degree days, base 60°F
2,232

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January87306
February696024
March523392
April28021234
May89126506
June4300747
July1410874
August2375838
September37174587
October24328283
November555168
December85109

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 37.1 km from Armstrong 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 USC00419380 (Vigo Park). Public domain.