Hyannis climate

Hyannis Frost Dates and Growing Season

NOAA 1991-2020 normals for Whitman 5 Ene, 27.2 km from Hyannis, elevation 3740 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Whitman 5 Ene. 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 155 days.

Median at 36°F
last May 14, 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 26May 22May 19May 16May 14May 11May 9May 6May 2
32°FMay 16May 12May 9May 6May 4May 2Apr 30Apr 27Apr 22
28°FMay 7May 3Apr 30Apr 29Apr 25Apr 22Apr 19Apr 15Apr 10
24°FApr 30Apr 25Apr 20Apr 17Apr 13Apr 10Apr 6Apr 2Mar 27
20°FApr 19Apr 14Apr 10Apr 6Apr 3Mar 31Mar 27Mar 21Mar 14
16°FApr 11Apr 5Apr 1Mar 29Mar 24Mar 19Mar 14Mar 9Mar 4

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 17Sep 21Sep 24Sep 26Sep 29Oct 1Oct 4Oct 7Oct 11
32°FSep 25Sep 29Oct 2Oct 5Oct 8Oct 10Oct 14Oct 17Oct 22
28°FOct 2Oct 7Oct 10Oct 14Oct 17Oct 20Oct 23Oct 26Oct 30
24°FOct 10Oct 15Oct 19Oct 22Oct 25Oct 28Oct 31Nov 4Nov 9
20°FOct 18Oct 23Oct 27Oct 31Nov 2Nov 6Nov 9Nov 13Nov 18
16°FOct 26Oct 31Nov 4Nov 8Nov 11Nov 14Nov 18Nov 22Nov 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°F153148143140136133129125119
32°F173168163159155151147143137
28°F193186181178174171166161154
24°F216208202197193188184178172
20°F237229223219213208203198190
16°F257247242237231227221214206

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
6,786
Cooling degree days, base 65°F
641
Growing degree days, base 40°F
4,690
Growing degree days, base 45°F
3,593
Growing degree days, base 50°F
2,644
Growing degree days, base 55°F
1,841
Growing degree days, base 60°F
1,171

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,20301
February1,03404
March862020
April594260
May31021227
June64103490
July8238695
August22203646
September15470379
October5194106
November851016
December1,16701

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 27.2 km from Hyannis. 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 USW00094079 (Whitman 5 Ene). Public domain.