Liberty climate

Liberty Frost Dates and Growing Season

NOAA 1991-2020 normals for Mckeesport, 1.6 km from Liberty, elevation 740 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mckeesport. 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 2 and the first fall freeze around October 20, a growing season of about 170 days.

Median at 36°F
last May 12, first October 7
Median at 32°F
last May 2, first October 20
Median at 28°F
last April 20, first November 1

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 27May 23May 19May 15May 12May 8May 4Apr 30Apr 26
32°FMay 20May 14May 10May 5May 2Apr 29Apr 26Apr 22Apr 17
28°FMay 10May 4Apr 29Apr 24Apr 20Apr 16Apr 13Apr 7Apr 2
24°FApr 30Apr 19Apr 13Apr 7Apr 4Apr 1Mar 29Mar 24Mar 18
20°FApr 10Apr 3Mar 31Mar 27Mar 22Mar 18Mar 15Mar 11Mar 4
16°FMar 30Mar 22Mar 18Mar 15Mar 10Mar 7Mar 3Feb 28Feb 19

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 21Sep 28Oct 2Oct 5Oct 7Oct 11Oct 14Oct 17Oct 24
32°FOct 1Oct 6Oct 11Oct 15Oct 20Oct 24Oct 27Oct 31Nov 3
28°FOct 10Oct 20Oct 25Oct 30Nov 1Nov 3Nov 6Nov 10Nov 14
24°FOct 28Nov 2Nov 5Nov 9Nov 12Nov 15Nov 18Nov 23Dec 1
20°FNov 8Nov 13Nov 18Nov 22Nov 26Nov 30Dec 3Dec 7Dec 16
16°FNov 18Nov 26Dec 1Dec 5Dec 10Dec 15Dec 20Dec 25Jan 1

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°F171163158153149145139134128
32°F192186179174170164159154144
28°F217210204198194188182176167
24°F246238232227222216211205194
20°F275266258253248243238231222
16°F302294287280274269262256247

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
5,580
Cooling degree days, base 65°F
767
Growing degree days, base 40°F
5,400
Growing degree days, base 45°F
4,177
Growing degree days, base 50°F
3,104
Growing degree days, base 55°F
2,179
Growing degree days, base 60°F
1,397

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,10004
February93205
March785030
April4315125
May18847336
June34151567
July3253714
August7216674
September8885449
October37110162
November678031
December96307

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 1.6 km from Liberty. 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 USC00365573 (Mckeesport). Public domain.