Stewartstown climate

Stewartstown Frost Dates and Growing Season

NOAA 1991-2020 normals for Colebrook 3SW, 16.3 km from Stewartstown, elevation 1120 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Colebrook 3SW. 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 31 and the first fall freeze around September 21, a growing season of about 112 days.

Median at 36°F
last June 10, first September 7
Median at 32°F
last May 31, first September 21
Median at 28°F
last May 17, first October 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°FJul 1Jun 22Jun 17Jun 13Jun 10Jun 7Jun 4Jun 1May 29
32°FJun 14Jun 8Jun 4Jun 2May 31May 28May 25May 21May 16
28°FMay 31May 26May 22May 20May 17May 14May 11May 7May 2
24°FMay 18May 13May 10May 7May 4May 1Apr 28Apr 25Apr 21
20°FMay 5Apr 30Apr 27Apr 24Apr 21Apr 18Apr 16Apr 13Apr 9
16°FApr 22Apr 19Apr 15Apr 13Apr 11Apr 9Apr 6Apr 4Apr 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°FAug 19Aug 28Sep 1Sep 3Sep 7Sep 10Sep 13Sep 17Sep 21
32°FSep 7Sep 11Sep 15Sep 18Sep 21Sep 23Sep 26Sep 29Oct 2
28°FSep 20Sep 23Sep 27Sep 29Oct 1Oct 3Oct 5Oct 8Oct 13
24°FSep 29Oct 2Oct 5Oct 7Oct 10Oct 14Oct 17Oct 22Oct 28
20°FOct 6Oct 11Oct 15Oct 19Oct 23Oct 27Oct 31Nov 2Nov 7
16°FOct 18Oct 25Oct 29Nov 1Nov 3Nov 6Nov 8Nov 12Nov 17

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°F10710095908681756858
32°F1301241191151121071039892
28°F155148143139135132128123117
24°F179173167162159154150144138
20°F202196191187182178173168161
16°F221215211208204201197192186

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
9,336
Cooling degree days, base 65°F
148
Growing degree days, base 40°F
3,167
Growing degree days, base 45°F
2,286
Growing degree days, base 50°F
1,527
Growing degree days, base 55°F
899
Growing degree days, base 60°F
431

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,63400
February1,43900
March1,28001
April815015
May4474114
June18330303
July7161456
August10540400
September29513203
October671034
November1,00203
December1,39500

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 16.3 km from Stewartstown. 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 USC00271647 (Colebrook 3SW). Public domain.