Rockland climate

Rockland Frost Dates and Growing Season

NOAA 1991-2020 normals for W Rockport 1 Nnw, 10.3 km from Rockland, elevation 361 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for W Rockport 1 Nnw. 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 April 27 and the first fall freeze around October 19, a growing season of about 175 days.

Median at 36°F
last May 8, first October 7
Median at 32°F
last April 27, first October 19
Median at 28°F
last April 15, first October 31

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 22May 17May 14May 11May 8May 5May 3May 1Apr 28
32°FMay 9May 4May 1Apr 29Apr 27Apr 25Apr 23Apr 21Apr 17
28°FApr 26Apr 22Apr 19Apr 17Apr 15Apr 12Apr 9Apr 7Apr 4
24°FApr 16Apr 11Apr 8Apr 6Apr 4Apr 3Apr 1Mar 31Mar 24
20°FApr 6Apr 4Apr 2Mar 31Mar 29Mar 26Mar 23Mar 19Mar 14
16°FApr 2Mar 31Mar 27Mar 24Mar 21Mar 18Mar 15Mar 12Mar 7

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 28Oct 1Oct 3Oct 6Oct 7Oct 10Oct 13Oct 17Oct 21
32°FOct 5Oct 9Oct 12Oct 15Oct 19Oct 22Oct 25Oct 29Nov 3
28°FOct 14Oct 21Oct 25Oct 28Oct 31Nov 2Nov 5Nov 8Nov 12
24°FOct 26Oct 31Nov 4Nov 8Nov 11Nov 13Nov 16Nov 20Nov 24
20°FNov 7Nov 13Nov 16Nov 19Nov 22Nov 25Nov 28Dec 1Dec 5
16°FNov 17Nov 23Nov 27Nov 30Dec 1Dec 4Dec 6Dec 10Dec 15

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°F170164160155152148145140134
32°F192186182179175170166162156
28°F215210205201197194190186179
24°F237231227223219216212207199
20°F258251246242238234230226219
16°F274267262259256251247242235

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
7,396
Cooling degree days, base 65°F
311
Growing degree days, base 40°F
3,954
Growing degree days, base 45°F
2,926
Growing degree days, base 50°F
2,043
Growing degree days, base 55°F
1,309
Growing degree days, base 60°F
727

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,35900
February1,17500
March1,05702
April675019
May3717141
June12640367
July26124563
August26111550
September16529318
October495173
November783010
December1,13800

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 10.3 km from Rockland. 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 USC00179593 (W Rockport 1 Nnw). Public domain.