Winchester climate

Winchester Frost Dates and Growing Season

NOAA 1991-2020 normals for Ripley Exp Farm, 21.4 km from Winchester, elevation 880 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ripley Exp Farm. 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 29 and the first fall freeze around October 11, a growing season of about 162 days.

Median at 36°F
last May 9, first October 1
Median at 32°F
last April 29, first October 11
Median at 28°F
last April 20, first October 21

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 26May 20May 16May 13May 9May 6May 3Apr 30Apr 25
32°FMay 16May 10May 6May 2Apr 29Apr 26Apr 23Apr 20Apr 17
28°FMay 8Apr 30Apr 27Apr 23Apr 20Apr 18Apr 15Apr 11Apr 6
24°FApr 24Apr 19Apr 15Apr 11Apr 8Apr 5Apr 3Mar 31Mar 26
20°FApr 13Apr 7Apr 4Apr 2Mar 31Mar 28Mar 23Mar 19Mar 12
16°FApr 4Mar 30Mar 26Mar 22Mar 18Mar 14Mar 11Mar 6Feb 28

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 18Sep 23Sep 26Sep 29Oct 1Oct 4Oct 6Oct 9Oct 13
32°FSep 28Oct 2Oct 5Oct 8Oct 11Oct 13Oct 16Oct 19Oct 23
28°FOct 7Oct 12Oct 15Oct 18Oct 21Oct 23Oct 26Oct 30Nov 3
24°FOct 17Oct 23Oct 27Oct 30Nov 1Nov 4Nov 8Nov 13Nov 18
20°FNov 1Nov 3Nov 7Nov 11Nov 14Nov 18Nov 21Nov 26Dec 2
16°FNov 9Nov 15Nov 20Nov 24Nov 29Dec 1Dec 4Dec 8Dec 15

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°F162156152149145141136131125
32°F179174170166162159155151143
28°F202196191187183178174169163
24°F228220215211206202198192185
20°F253246241237233227223217208
16°F279270264259254249244239233

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
5,620
Cooling degree days, base 65°F
778
Growing degree days, base 40°F
5,463
Growing degree days, base 45°F
4,251
Growing degree days, base 50°F
3,172
Growing degree days, base 55°F
2,230
Growing degree days, base 60°F
1,428

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13606
February93104
March774033
April4197139
May16353364
June29164585
July2253716
August7212669
September9080442
October3779166
November688142
December1,00406

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 21.4 km from Winchester. 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 USC00337120 (Ripley Exp Farm). Public domain.