Ferrisburgh climate

Ferrisburgh Frost Dates and Growing Season

NOAA 1991-2020 normals for Vergennes, 3.8 km from Ferrisburgh, elevation 196 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Vergennes. 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 30 and the first fall freeze around October 17, a growing season of about 168 days.

Median at 36°F
last May 9, first October 5
Median at 32°F
last April 30, first October 17
Median at 28°F
last April 21, first October 30

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

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 23Sep 27Sep 30Oct 2Oct 5Oct 7Oct 10Oct 14Oct 18
32°FOct 2Oct 6Oct 10Oct 14Oct 17Oct 20Oct 23Oct 27Nov 1
28°FOct 14Oct 20Oct 24Oct 27Oct 30Nov 1Nov 4Nov 7Nov 12
24°FOct 27Nov 1Nov 4Nov 6Nov 9Nov 12Nov 15Nov 18Nov 24
20°FNov 6Nov 10Nov 14Nov 17Nov 19Nov 22Nov 25Nov 28Dec 3
16°FNov 14Nov 19Nov 22Nov 25Nov 28Dec 1Dec 3Dec 7Dec 12

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°F163158153149146143138134128
32°F187180175172168165161156149
28°F209203199196192188184180173
24°F230223219216213210205201194
20°F248242238234230226222218212
16°F264258253250246242238233228

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
7,345
Cooling degree days, base 65°F
563
Growing degree days, base 40°F
4,477
Growing degree days, base 45°F
3,435
Growing degree days, base 50°F
2,520
Growing degree days, base 55°F
1,735
Growing degree days, base 60°F
1,081

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,41400
February1,23100
March1,074111
April621139
May28119231
June66103488
July9217672
August15165615
September15855355
October485394
November813014
December1,17800

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 3.8 km from Ferrisburgh. 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 USC00438597 (Vergennes). Public domain.