Gettysburg climate

Gettysburg Frost Dates and Growing Season

NOAA 1991-2020 normals for Eisenhower Nhs, 2.9 km from Gettysburg, elevation 540 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Eisenhower Nhs. 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 24 and the first fall freeze around October 21, a growing season of about 180 days.

Median at 36°F
last May 5, first October 10
Median at 32°F
last April 24, first October 21
Median at 28°F
last April 7, 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 21May 16May 12May 8May 5May 2Apr 29Apr 25Apr 21
32°FMay 10May 4Apr 30Apr 27Apr 24Apr 21Apr 17Apr 13Apr 7
28°FApr 27Apr 20Apr 15Apr 11Apr 7Apr 5Apr 3Mar 31Mar 26
24°FApr 9Apr 4Apr 1Mar 30Mar 27Mar 24Mar 20Mar 16Mar 10
20°FMar 30Mar 25Mar 21Mar 18Mar 14Mar 11Mar 7Mar 3Feb 26
16°FMar 23Mar 16Mar 12Mar 8Mar 4Mar 1Feb 26Feb 21Feb 15

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 26Oct 1Oct 4Oct 6Oct 10Oct 12Oct 16Oct 19Oct 25
32°FOct 6Oct 11Oct 15Oct 18Oct 21Oct 24Oct 27Oct 31Nov 4
28°FOct 16Oct 23Oct 26Oct 29Nov 1Nov 3Nov 6Nov 10Nov 15
24°FOct 30Nov 2Nov 5Nov 8Nov 12Nov 14Nov 19Nov 23Nov 30
20°FNov 8Nov 13Nov 16Nov 20Nov 24Nov 29Dec 3Dec 7Dec 16
16°FNov 17Nov 25Dec 1Dec 5Dec 10Dec 16Dec 21Dec 27Jan 4

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°F177171165160157152148143134
32°F201194188184180176170165158
28°F224218213209205201197191183
24°F254246240235230225221216208
20°F279271264259255250244240232
16°F305298292285280275269261253

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
5,277
Cooling degree days, base 65°F
871
Growing degree days, base 40°F
5,628
Growing degree days, base 45°F
4,377
Growing degree days, base 50°F
3,276
Growing degree days, base 55°F
2,325
Growing degree days, base 60°F
1,522

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,07903
February90302
March740126
April3987137
May16749351
June30168588
July1295759
August4244705
September6895478
October33712180
November632041
December91907

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 2.9 km from Gettysburg. 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 USC00362537 (Eisenhower Nhs). Public domain.