Morristown climate

Morristown Frost Dates and Growing Season

NOAA 1991-2020 normals for Morrisville Stowe State AP, 2.6 km from Morristown, elevation 732 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Morrisville Stowe State AP. 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 20 and the first fall freeze around September 28, a growing season of about 129 days.

Median at 36°F
last June 2, first September 16
Median at 32°F
last May 20, first September 28
Median at 28°F
last May 7, first October 7

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°FJun 14Jun 10Jun 7Jun 4Jun 2May 30May 28May 24May 19
32°FJun 4May 30May 27May 23May 20May 17May 14May 11May 6
28°FMay 23May 18May 14May 10May 7May 4May 1Apr 29Apr 25
24°FMay 8May 4May 1Apr 30Apr 27Apr 24Apr 22Apr 18Apr 14
20°FApr 27Apr 22Apr 18Apr 15Apr 13Apr 10Apr 7Apr 5Apr 2
16°FApr 15Apr 11Apr 8Apr 6Apr 4Apr 2Mar 31Mar 29Mar 23

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 4Sep 8Sep 11Sep 14Sep 16Sep 19Sep 22Sep 25Sep 29
32°FSep 14Sep 19Sep 22Sep 25Sep 28Sep 30Oct 2Oct 5Oct 10
28°FSep 26Oct 1Oct 2Oct 5Oct 7Oct 10Oct 14Oct 18Oct 24
24°FOct 4Oct 8Oct 13Oct 17Oct 20Oct 23Oct 28Nov 1Nov 5
20°FOct 16Oct 22Oct 26Oct 31Nov 2Nov 5Nov 8Nov 12Nov 16
16°FOct 31Nov 3Nov 6Nov 10Nov 13Nov 15Nov 18Nov 21Nov 25

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°F123116112109105102989487
32°F149142136133129125120116110
28°F172166161157153149144139133
24°F197190185181177174169164157
20°F220214210205201198194190183
16°F240233229224221217213209202

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
8,417
Cooling degree days, base 65°F
245
Growing degree days, base 40°F
3,618
Growing degree days, base 45°F
2,671
Growing degree days, base 50°F
1,849
Growing degree days, base 55°F
1,154
Growing degree days, base 60°F
608

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,52800
February1,32000
March1,16103
April728125
May3748156
June13144365
July3898525
August6872470
September24122251
October600051
November92305
December1,30700

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 Morristown. 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 USW00054771 (Morrisville Stowe State AP). Public domain.