Jamestown climate

Jamestown Frost Dates and Growing Season

NOAA 1991-2020 normals for Jamestown 2 E, 2.6 km from Jamestown, elevation 962 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jamestown 2 E. 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 23 and the first fall freeze around October 19, a growing season of about 178 days.

Median at 36°F
last May 3, first October 9
Median at 32°F
last April 23, first October 19
Median at 28°F
last April 9, 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 15May 10May 6May 3Apr 30Apr 28Apr 24Apr 19
32°FMay 9May 2Apr 29Apr 25Apr 23Apr 19Apr 16Apr 13Apr 8
28°FApr 28Apr 21Apr 17Apr 13Apr 9Apr 6Apr 4Apr 1Mar 26
24°FApr 15Apr 8Apr 4Apr 1Mar 31Mar 28Mar 23Mar 18Mar 12
20°FApr 3Mar 31Mar 26Mar 21Mar 18Mar 15Mar 11Mar 8Mar 2
16°FMar 26Mar 18Mar 15Mar 12Mar 9Mar 6Mar 2Feb 26Feb 18

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 25Sep 30Oct 4Oct 6Oct 9Oct 12Oct 14Oct 18Oct 22
32°FOct 4Oct 11Oct 14Oct 17Oct 19Oct 22Oct 25Oct 28Nov 1
28°FOct 18Oct 22Oct 26Oct 29Nov 1Nov 2Nov 5Nov 9Nov 14
24°FOct 30Nov 1Nov 4Nov 7Nov 10Nov 13Nov 17Nov 22Nov 28
20°FNov 6Nov 10Nov 14Nov 18Nov 22Nov 25Nov 30Dec 4Dec 11
16°FNov 12Nov 19Nov 24Nov 28Dec 1Dec 5Dec 10Dec 15Dec 21

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°F177170166161157153148143136
32°F198192187183178174170163155
28°F225218212207204199195188180
24°F249241236232227223218213205
20°F272264258253249243239234226
16°F293285280274268263258252242

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
5,850
Cooling degree days, base 65°F
840
Growing degree days, base 40°F
5,495
Growing degree days, base 45°F
4,302
Growing degree days, base 50°F
3,243
Growing degree days, base 55°F
2,305
Growing degree days, base 60°F
1,503

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21702
February99703
March794240
April4337133
May16765374
June26185609
July4250711
August8212670
September84102470
October35616190
November709136
December1,05704

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 2.6 km from Jamestown. 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 USC00124356 (Jamestown 2 E). Public domain.