Rockport climate

Rockport Frost Dates and Growing Season

NOAA 1991-2020 normals for Rockport, 0.3 km from Rockport, elevation 8 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rockport. 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 January 31 and the first fall freeze around December 25, a growing season of about 328 days.

Median at 36°F
last February 16, first December 6
Median at 32°F
last January 31, first December 25
Median at 28°F
last January 20, first January 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°FMar 10Mar 3Feb 27Feb 22Feb 16Feb 10Feb 4Jan 28Jan 18
32°FFeb 28Feb 19Feb 11Feb 5Jan 31Jan 25Jan 17Jan 7Dec 26
28°FFeb 20Feb 8Feb 2Jan 28Jan 20Jan 12Jan 6Dec 31Dec 19
24°FFeb 6Jan 28Jan 17Jan 11Jan 7Jan 2Dec 31Dec 25Dec 18
20°F–––––––––
16°F–––––––––

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°FNov 15Nov 22Nov 29Dec 2Dec 6Dec 11Dec 18Dec 26Jan 3
32°FNov 28Dec 5Dec 11Dec 19Dec 25Dec 31Jan 4Jan 12Jan 31
28°FDec 11Dec 20Dec 28Jan 1Jan 5Jan 9Jan 16Jan 30Feb 8
24°FDec 15Dec 24Dec 28Jan 1Jan 4Jan 7Jan 10Jan 23Feb 2
20°F–––––––––
16°F–––––––––

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°F330318308302295288280273262
32°F365353343334328321311302289
28°F365365365365364355344335322
24°F365365365365365365365365356
20°F365365365365365365365365365
16°F365365365365365365365365365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
99% of years
32°F or colder
89% of years
28°F or colder
53% of years
24°F or colder
18% of years
20°F or colder
5% of years
16°F or colder
0% 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
918
Cooling degree days, base 65°F
3,641
Growing degree days, base 40°F
11,855
Growing degree days, base 45°F
10,050
Growing degree days, base 50°F
8,283
Growing degree days, base 55°F
6,598
Growing degree days, base 60°F
5,043

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January29412218
February18126281
March8094483
April13235672
May0427891
June05681,018
July06321,097
August06491,114
September0526976
October12331784
November93111474
December24530274

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 0.3 km from Rockport. 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 USC00417704 (Rockport). Public domain.