Mount Hermon climate

Mount Hermon Frost Dates and Growing Season

NOAA 1991-2020 normals for Danville 2 Se, 13.9 km from Mount Hermon, elevation 392 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Danville 2 Se. 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 8 and the first fall freeze around November 1, a growing season of about 205 days.

Median at 36°F
last April 21, first October 23
Median at 32°F
last April 8, first November 1
Median at 28°F
last March 27, first November 10

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 8May 3Apr 30Apr 25Apr 21Apr 19Apr 16Apr 12Apr 5
32°FApr 30Apr 19Apr 15Apr 11Apr 8Apr 4Apr 1Mar 29Mar 22
28°FApr 10Apr 4Apr 1Mar 30Mar 27Mar 24Mar 19Mar 15Mar 8
24°FMar 29Mar 24Mar 19Mar 17Mar 14Mar 10Mar 5Feb 28Feb 21
20°FMar 19Mar 14Mar 10Mar 4Mar 1Feb 24Feb 18Feb 11Feb 2
16°FMar 11Mar 3Feb 24Feb 17Feb 10Feb 4Jan 31Jan 24Jan 11

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 11Oct 15Oct 19Oct 22Oct 23Oct 26Oct 28Oct 31Nov 3
32°FOct 19Oct 23Oct 27Oct 30Nov 1Nov 2Nov 5Nov 8Nov 13
28°FOct 29Nov 1Nov 4Nov 6Nov 10Nov 13Nov 16Nov 21Nov 27
24°FNov 7Nov 12Nov 16Nov 20Nov 24Nov 28Dec 1Dec 5Dec 14
20°FNov 18Nov 25Dec 1Dec 4Dec 9Dec 15Dec 20Dec 28Jan 3
16°FDec 5Dec 13Dec 21Dec 27Jan 1Jan 4Jan 10Jan 16Jan 30

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°F204197192187183179175170163
32°F226219213209205201197191183
28°F251243237233229225220214208
24°F281273266261256250245239231
20°F314304297291284278271264254
16°F351339331324316308301295282

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
96% 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
3,832
Cooling degree days, base 65°F
1,525
Growing degree days, base 40°F
7,171
Growing degree days, base 45°F
5,718
Growing degree days, base 50°F
4,433
Growing degree days, base 55°F
3,309
Growing degree days, base 60°F
2,343

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January834012
February671018
March527388
April24131265
May72125519
June7302745
July0440905
August0389854
September25199624
October21132300
November502282
December743120

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 13.9 km from Mount Hermon. 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 USC00442245 (Danville 2 Se). Public domain.