Hershey climate

Hershey Frost Dates and Growing Season

NOAA 1991-2020 normals for Hershey 5 Sse, 6.3 km from Hershey, elevation 2952 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hershey 5 Sse. 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 4 and the first fall freeze around October 9, a growing season of about 156 days.

Median at 36°F
last May 12, first September 30
Median at 32°F
last May 4, first October 9
Median at 28°F
last April 24, first October 19

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 29May 22May 18May 15May 12May 10May 8May 6May 2
32°FMay 16May 12May 9May 6May 4May 2Apr 30Apr 26Apr 21
28°FMay 7May 3Apr 30Apr 27Apr 24Apr 22Apr 18Apr 14Apr 10
24°FApr 28Apr 23Apr 19Apr 16Apr 12Apr 9Apr 6Apr 2Mar 28
20°FApr 18Apr 13Apr 9Apr 6Apr 3Mar 31Mar 26Mar 21Mar 14
16°FApr 10Apr 4Apr 1Mar 27Mar 23Mar 20Mar 14Mar 10Mar 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°FSep 15Sep 20Sep 24Sep 27Sep 30Oct 3Oct 5Oct 8Oct 12
32°FSep 23Sep 30Oct 3Oct 6Oct 9Oct 12Oct 14Oct 17Oct 21
28°FOct 4Oct 10Oct 13Oct 16Oct 19Oct 21Oct 23Oct 26Oct 30
24°FOct 14Oct 18Oct 21Oct 24Oct 26Oct 29Nov 1Nov 4Nov 9
20°FOct 20Oct 25Oct 29Nov 1Nov 3Nov 6Nov 9Nov 12Nov 18
16°FOct 28Nov 1Nov 5Nov 9Nov 12Nov 16Nov 19Nov 23Nov 28

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°F155150145141138135130125119
32°F174168164160156153148144137
28°F194187182178175171167163155
24°F216209203200196191187181175
20°F236228223218213209204198190
16°F257249243238233228222216207

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
6,390
Cooling degree days, base 65°F
808
Growing degree days, base 40°F
5,085
Growing degree days, base 45°F
3,950
Growing degree days, base 50°F
2,957
Growing degree days, base 55°F
2,108
Growing degree days, base 60°F
1,393

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18901
February1,00102
March820020
April534277
May25429271
June39148561
July6295755
August12241694
September11886426
October4546133
November821016
December1,14400

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 6.3 km from Hershey. 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 USC00253810 (Hershey 5 Sse). Public domain.