Bartlett climate

Bartlett Frost Dates and Growing Season

NOAA 1991-2020 normals for Bartlett 1W, 0.9 km from Bartlett, elevation 2175 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bartlett 1W. 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 4 and the first fall freeze around October 8, a growing season of about 154 days.

Median at 36°F
last May 15, first September 29
Median at 32°F
last May 4, first October 8
Median at 28°F
last April 25, first October 17

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 29May 24May 21May 17May 15May 12May 8May 5May 1
32°FMay 20May 15May 11May 7May 4May 1Apr 29Apr 25Apr 20
28°FMay 10May 5May 1Apr 29Apr 25Apr 22Apr 18Apr 13Apr 8
24°FMay 1Apr 26Apr 21Apr 17Apr 13Apr 9Apr 6Apr 2Mar 28
20°FApr 20Apr 14Apr 10Apr 6Apr 3Mar 31Mar 28Mar 23Mar 15
16°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 19Mar 15Mar 11Mar 5

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 14Sep 19Sep 23Sep 27Sep 29Oct 1Oct 4Oct 7Oct 12
32°FSep 21Sep 28Oct 1Oct 4Oct 8Oct 11Oct 13Oct 17Oct 22
28°FOct 1Oct 6Oct 10Oct 14Oct 17Oct 20Oct 23Oct 26Oct 31
24°FOct 12Oct 16Oct 20Oct 23Oct 27Oct 30Nov 2Nov 5Nov 11
20°FOct 18Oct 25Oct 30Nov 2Nov 5Nov 8Nov 11Nov 15Nov 20
16°FOct 28Nov 1Nov 5Nov 9Nov 13Nov 17Nov 21Nov 24Nov 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°F155148144140137132128122114
32°F176169163158154150145140132
28°F197189184179174170164159151
24°F217210204199195190185178170
20°F237229223218214210205200192
16°F256249243236232227222216207

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
6,543
Cooling degree days, base 65°F
929
Growing degree days, base 40°F
5,255
Growing degree days, base 45°F
4,124
Growing degree days, base 50°F
3,131
Growing degree days, base 55°F
2,267
Growing degree days, base 60°F
1,533

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,28800
February1,06103
March844126
April509493
May23045304
June36193608
July6322781
August12258711
September11497442
October4389145
November824019
December1,18201

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 0.9 km from Bartlett. 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 USC00250525 (Bartlett 1W). Public domain.