Mount Jewett climate

Mount Jewett Frost Dates and Growing Season

NOAA 1991-2020 normals for Clermont 1 Nw, 12 km from Mount Jewett, elevation 2080 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Clermont 1 Nw. 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 15 and the first fall freeze around October 3, a growing season of about 140 days.

Median at 36°F
last May 29, first September 23
Median at 32°F
last May 15, first October 3
Median at 28°F
last May 4, first October 16

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 11Jun 6Jun 2May 31May 29May 25May 22May 19May 13
32°FMay 31May 26May 22May 19May 15May 11May 8May 4Apr 30
28°FMay 20May 15May 10May 6May 4Apr 30Apr 27Apr 23Apr 19
24°FMay 7May 1Apr 28Apr 24Apr 21Apr 18Apr 15Apr 11Apr 7
20°FApr 23Apr 18Apr 15Apr 11Apr 7Apr 5Apr 3Mar 31Mar 26
16°FApr 13Apr 7Apr 4Apr 1Mar 31Mar 28Mar 24Mar 20Mar 15

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 6Sep 14Sep 17Sep 21Sep 23Sep 25Sep 29Oct 1Oct 4
32°FSep 21Sep 25Sep 29Oct 1Oct 3Oct 6Oct 9Oct 12Oct 18
28°FOct 1Oct 5Oct 10Oct 13Oct 16Oct 20Oct 23Oct 27Nov 1
24°FOct 13Oct 19Oct 23Oct 27Oct 31Nov 2Nov 5Nov 9Nov 15
20°FOct 28Nov 1Nov 5Nov 8Nov 12Nov 15Nov 18Nov 23Nov 29
16°FNov 6Nov 12Nov 16Nov 20Nov 23Nov 27Dec 1Dec 4Dec 10

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°F13612912411911611310810395
32°F162154149145140136132127121
28°F188181175169165161156151142
24°F213206200195192187182176168
20°F239231225221217212208202195
16°F260252247242237233228223216

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
7,752
Cooling degree days, base 65°F
184
Growing degree days, base 40°F
3,680
Growing degree days, base 45°F
2,671
Growing degree days, base 50°F
1,804
Growing degree days, base 55°F
1,080
Growing degree days, base 60°F
533

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,35601
February1,17601
March1,05408
April655146
May35010182
June13138360
July5975480
August8347429
September25712224
October572165
November87008
December1,19001

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 12 km from Mount Jewett. 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 USC00361526 (Clermont 1 Nw). Public domain.