Loretto climate

Loretto Frost Dates and Growing Season

NOAA 1991-2020 normals for Lexington, 14.2 km from Loretto, elevation 760 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lexington. 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 March 29 and the first fall freeze around November 4, a growing season of about 219 days.

Median at 36°F
last April 10, first October 26
Median at 32°F
last March 29, first November 4
Median at 28°F
last March 15, first November 16

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°FApr 26Apr 21Apr 16Apr 13Apr 10Apr 7Apr 4Mar 31Mar 25
32°FApr 15Apr 9Apr 5Apr 1Mar 29Mar 25Mar 21Mar 17Mar 10
28°FApr 3Mar 30Mar 24Mar 19Mar 15Mar 12Mar 7Mar 2Feb 24
24°FMar 23Mar 16Mar 10Mar 6Mar 2Feb 26Feb 22Feb 16Feb 9
20°FMar 12Mar 5Feb 28Feb 23Feb 17Feb 12Feb 6Jan 31Jan 22
16°FFeb 28Feb 19Feb 11Feb 5Jan 31Jan 28Jan 22Jan 15Jan 5

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 14Oct 17Oct 20Oct 23Oct 26Oct 28Oct 31Nov 2Nov 7
32°FOct 21Oct 25Oct 30Nov 1Nov 4Nov 7Nov 10Nov 15Nov 23
28°FNov 1Nov 5Nov 9Nov 12Nov 16Nov 20Nov 25Dec 1Dec 7
24°FNov 10Nov 17Nov 23Nov 28Dec 1Dec 5Dec 10Dec 20Dec 30
20°FNov 23Dec 1Dec 7Dec 13Dec 21Dec 26Jan 1Jan 5Jan 15
16°FDec 5Dec 14Dec 25Jan 1Jan 3Jan 8Jan 13Jan 18Jan 31

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°F219211206201197192189184178
32°F245236229224219215210205197
28°F273263256250245240234228218
24°F306294286280274268262254245
20°F335324316310305299293284273
16°F365354345336332325318308300

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
99% of years
16°F or colder
89% 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
3,188
Cooling degree days, base 65°F
1,765
Growing degree days, base 40°F
7,991
Growing degree days, base 45°F
6,440
Growing degree days, base 50°F
5,031
Growing degree days, base 55°F
3,775
Growing degree days, base 60°F
2,689

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January750039
February575358
March39612167
April16547343
May45160580
June1346795
July0448913
August0431896
September13253690
October16360372
November4276121
December652158

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 14.2 km from Loretto. 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 USC00010260 (Lexington). Public domain.