Jamestown climate

Jamestown Frost Dates and Growing Season

NOAA 1991-2020 normals for Jamestown Wwtp, 2.3 km from Jamestown, elevation 890 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jamestown Wwtp. 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 18 and the first fall freeze around October 24, a growing season of about 189 days.

Median at 36°F
last April 28, first October 15
Median at 32°F
last April 18, first October 24
Median at 28°F
last April 6, first November 2

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 12May 6May 3Apr 30Apr 28Apr 25Apr 22Apr 18Apr 14
32°FMay 3Apr 29Apr 25Apr 21Apr 18Apr 15Apr 12Apr 8Apr 2
28°FApr 25Apr 19Apr 15Apr 10Apr 6Apr 3Mar 31Mar 27Mar 20
24°FApr 14Apr 7Apr 3Mar 31Mar 27Mar 23Mar 18Mar 13Mar 5
20°FApr 4Mar 30Mar 24Mar 18Mar 14Mar 9Mar 4Feb 27Feb 19
16°FMar 22Mar 13Mar 7Mar 2Feb 27Feb 22Feb 17Feb 11Feb 2

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°FOct 2Oct 6Oct 10Oct 12Oct 15Oct 17Oct 20Oct 23Oct 27
32°FOct 11Oct 16Oct 20Oct 22Oct 24Oct 27Oct 30Nov 1Nov 5
28°FOct 21Oct 25Oct 29Nov 1Nov 2Nov 5Nov 7Nov 10Nov 15
24°FOct 31Nov 3Nov 5Nov 8Nov 11Nov 14Nov 18Nov 23Nov 30
20°FNov 8Nov 13Nov 16Nov 20Nov 24Nov 28Dec 1Dec 6Dec 15
16°FNov 16Nov 24Nov 30Dec 4Dec 9Dec 15Dec 22Dec 28Jan 5

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°F189182177173169165160156150
32°F208202197193189185181175169
28°F231224218214210206201196189
24°F257247242236232228223216208
20°F287276268262256251245238230
16°F316307299293288281273265253

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
4,541
Cooling degree days, base 65°F
1,083
Growing degree days, base 40°F
6,364
Growing degree days, base 45°F
5,006
Growing degree days, base 50°F
3,803
Growing degree days, base 55°F
2,747
Growing degree days, base 60°F
1,840

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January961013
February770020
March607372
April32015205
May11085445
June11216655
July1324787
August3286749
September50131532
October27922245
November598157
December831022

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 2.3 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 USC00154208 (Jamestown Wwtp). Public domain.