Palmyra climate

Palmyra Frost Dates and Growing Season

NOAA 1991-2020 normals for Lebanon 2 W, 11 km from Palmyra, elevation 450 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lebanon 2 W. 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 20 and the first fall freeze around October 25, a growing season of about 185 days.

Median at 36°F
last May 2, first October 14
Median at 32°F
last April 20, 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 18May 12May 9May 5May 2Apr 29Apr 27Apr 23Apr 18
32°FMay 7May 1Apr 27Apr 23Apr 20Apr 17Apr 14Apr 10Apr 5
28°FApr 18Apr 14Apr 10Apr 7Apr 4Apr 2Mar 31Mar 27Mar 22
24°FApr 5Apr 1Mar 30Mar 27Mar 23Mar 20Mar 16Mar 12Mar 6
20°FMar 28Mar 22Mar 18Mar 15Mar 12Mar 8Mar 5Mar 1Feb 24
16°FMar 18Mar 13Mar 9Mar 6Mar 2Feb 28Feb 23Feb 18Feb 10

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 1Oct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 23Oct 28
32°FOct 10Oct 15Oct 19Oct 22Oct 25Oct 28Oct 31Nov 2Nov 6
28°FOct 22Oct 27Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15Nov 20
24°FNov 3Nov 7Nov 11Nov 14Nov 17Nov 21Nov 24Nov 30Dec 4
20°FNov 13Nov 18Nov 23Nov 28Dec 1Dec 5Dec 9Dec 15Dec 22
16°FNov 28Dec 3Dec 7Dec 13Dec 19Dec 23Dec 27Dec 31Jan 7

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°F183177172168164160156151144
32°F206199194190185181177172166
28°F234227221216212209205199192
24°F262255249244240235231226219
20°F289280275269264259255249242
16°F314305299294289284279272265

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
5,455
Cooling degree days, base 65°F
856
Growing degree days, base 40°F
5,513
Growing degree days, base 45°F
4,290
Growing degree days, base 50°F
3,214
Growing degree days, base 55°F
2,285
Growing degree days, base 60°F
1,497

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,10002
February92702
March774021
April4216118
May16650353
June25170596
July1289753
August5238698
September7893466
October35211171
November656030
December95204

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 11 km from Palmyra. 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 USC00364896 (Lebanon 2 W). Public domain.