Burlington climate

Burlington Frost Dates and Growing Season

NOAA 1991-2020 normals for Burlington, 0.7 km from Burlington, elevation 4162 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Burlington. 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 6 and the first fall freeze around October 9, a growing season of about 155 days.

Median at 36°F
last May 15, first October 1
Median at 32°F
last May 6, first October 9
Median at 28°F
last April 27, first October 18

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 27May 23May 20May 17May 15May 13May 11May 8May 4
32°FMay 19May 14May 11May 9May 6May 3May 1Apr 28Apr 23
28°FMay 9May 5May 2Apr 30Apr 27Apr 24Apr 21Apr 17Apr 13
24°FApr 29Apr 25Apr 21Apr 19Apr 16Apr 13Apr 9Apr 5Mar 31
20°FApr 20Apr 15Apr 11Apr 7Apr 5Apr 2Mar 30Mar 25Mar 19
16°FApr 11Apr 6Apr 2Mar 31Mar 27Mar 23Mar 17Mar 11Mar 6

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 19Sep 24Sep 27Sep 29Oct 1Oct 4Oct 5Oct 8Oct 12
32°FSep 27Oct 1Oct 4Oct 6Oct 9Oct 12Oct 14Oct 17Oct 20
28°FOct 4Oct 9Oct 12Oct 15Oct 18Oct 20Oct 22Oct 25Oct 29
24°FOct 13Oct 18Oct 20Oct 23Oct 26Oct 29Nov 1Nov 3Nov 8
20°FOct 20Oct 25Oct 29Nov 1Nov 3Nov 6Nov 9Nov 13Nov 18
16°FOct 26Nov 1Nov 5Nov 9Nov 12Nov 16Nov 20Nov 24Nov 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°F154149145142139136131127121
32°F171166162158155152148144138
28°F191185181177173170166161155
24°F213205200196192188184179173
20°F232225220215210207201197191
16°F255246240234229224218213204

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
5,774
Cooling degree days, base 65°F
945
Growing degree days, base 40°F
5,496
Growing degree days, base 45°F
4,290
Growing degree days, base 50°F
3,235
Growing degree days, base 55°F
2,333
Growing degree days, base 60°F
1,572

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06801
February90705
March732035
April4873102
May22441310
June32191609
July4330790
August9266722
September99107466
October4108165
November752028
December1,05102

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 0.7 km from Burlington. 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 USC00051121 (Burlington). Public domain.