York County climate

York County Frost Dates and Growing Season

NOAA 1991-2020 normals for York, 0.7 km from York County, elevation 1610 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for York. 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 22 and the first fall freeze around October 18, a growing season of about 178 days.

Median at 36°F
last May 2, first October 8
Median at 32°F
last April 22, first October 18
Median at 28°F
last April 10, first October 26

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 14May 10May 7May 4May 2Apr 30Apr 27Apr 23Apr 17
32°FMay 5May 1Apr 29Apr 25Apr 22Apr 19Apr 15Apr 11Apr 6
28°FApr 26Apr 21Apr 17Apr 13Apr 10Apr 7Apr 4Apr 1Mar 27
24°FApr 17Apr 10Apr 7Apr 4Apr 1Mar 30Mar 26Mar 22Mar 16
20°FApr 7Apr 2Mar 31Mar 28Mar 24Mar 21Mar 17Mar 12Mar 7
16°FApr 1Mar 27Mar 23Mar 19Mar 14Mar 11Mar 6Mar 3Feb 27

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 24Sep 29Oct 2Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20
32°FOct 1Oct 8Oct 13Oct 15Oct 18Oct 20Oct 22Oct 25Oct 28
28°FOct 13Oct 18Oct 21Oct 24Oct 26Oct 29Nov 1Nov 3Nov 9
24°FOct 21Oct 26Oct 30Nov 1Nov 4Nov 6Nov 10Nov 13Nov 19
20°FOct 29Nov 2Nov 6Nov 9Nov 12Nov 15Nov 18Nov 23Nov 28
16°FNov 2Nov 9Nov 13Nov 17Nov 21Nov 24Nov 27Dec 1Dec 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°F178171166162158154151146139
32°F196190185181178173169164157
28°F216209205201197193188183175
24°F238230224220216212207202195
20°F256248243238233228224218210
16°F274267260255251246241235226

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
6,144
Cooling degree days, base 65°F
1,129
Growing degree days, base 40°F
5,703
Growing degree days, base 45°F
4,539
Growing degree days, base 50°F
3,496
Growing degree days, base 55°F
2,583
Growing degree days, base 60°F
1,792

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27100
February1,03002
March800030
April4509125
May17562363
June19254685
July2370834
August6291750
September84124494
October38117184
November783029
December1,14201

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 0.7 km from York County. 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 USC00259510 (York). Public domain.