Chittenden climate

Chittenden Frost Dates and Growing Season

NOAA 1991-2020 normals for Rutland, 9.5 km from Chittenden, elevation 620 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rutland. 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 September 27, a growing season of about 132 days.

Median at 36°F
last May 29, first September 16
Median at 32°F
last May 15, first September 27
Median at 28°F
last May 2, first October 5

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 10Jun 6Jun 3May 31May 29May 26May 22May 19May 13
32°FMay 31May 25May 22May 18May 15May 12May 8May 5May 1
28°FMay 16May 12May 7May 4May 2Apr 30Apr 28Apr 25Apr 22
24°FMay 4Apr 30Apr 26Apr 23Apr 21Apr 19Apr 16Apr 11Apr 6
20°FApr 21Apr 18Apr 15Apr 12Apr 9Apr 6Apr 4Apr 2Mar 30
16°FApr 14Apr 9Apr 5Apr 3Apr 1Mar 31Mar 28Mar 24Mar 18

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 10Sep 13Sep 16Sep 18Sep 21Sep 25Sep 29
32°FSep 13Sep 17Sep 21Sep 24Sep 27Sep 29Oct 1Oct 4Oct 8
28°FSep 23Sep 28Oct 1Oct 3Oct 5Oct 7Oct 11Oct 15Oct 21
24°FOct 3Oct 7Oct 11Oct 15Oct 18Oct 22Oct 26Oct 31Nov 4
20°FOct 15Oct 21Oct 25Oct 28Nov 1Nov 3Nov 6Nov 11Nov 16
16°FOct 30Nov 2Nov 5Nov 10Nov 13Nov 16Nov 19Nov 23Nov 28

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°F1291231181131101071039993
32°F151145140136132129124118112
28°F175167162158155151147142136
24°F202194189184179175171166160
20°F224217212208204200196190184
16°F246238233229224221217212205

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
7,807
Cooling degree days, base 65°F
311
Growing degree days, base 40°F
3,916
Growing degree days, base 45°F
2,919
Growing degree days, base 50°F
2,056
Growing degree days, base 55°F
1,320
Growing degree days, base 60°F
731

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,43500
February1,24700
March1,09403
April664138
May32012196
June10061412
July24128569
August4887504
September22322265
October565159
November86709
December1,21800

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 9.5 km from Chittenden. 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 USC00436995 (Rutland). Public domain.