Atlantic climate

Atlantic Frost Dates and Growing Season

NOAA 1991-2020 normals for Cedar Is, 11.5 km from Atlantic, elevation 8 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cedar Is. 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 March 11 and the first fall freeze around November 30, a growing season of about 261 days.

Median at 36°F
last March 24, first November 17
Median at 32°F
last March 11, first November 30
Median at 28°F
last February 27, first December 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°FApr 9Apr 4Mar 31Mar 28Mar 24Mar 20Mar 17Mar 13Mar 5
32°FMar 30Mar 23Mar 19Mar 15Mar 11Mar 8Mar 3Feb 27Feb 19
28°FMar 19Mar 12Mar 7Mar 3Feb 27Feb 22Feb 14Feb 5Jan 29
24°FMar 4Feb 26Feb 19Feb 11Feb 5Jan 31Jan 26Jan 17Jan 8
20°FFeb 17Feb 8Feb 1Jan 30Jan 26Jan 21Jan 17Jan 10Jan 1
16°FFeb 15Feb 1Jan 30Jan 27Jan 23Jan 19Jan 15Jan 11Jan 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°FNov 1Nov 6Nov 10Nov 14Nov 17Nov 20Nov 23Nov 28Dec 2
32°FNov 11Nov 18Nov 22Nov 26Nov 30Dec 2Dec 6Dec 13Dec 20
28°FNov 24Dec 1Dec 6Dec 11Dec 17Dec 23Dec 29Jan 4Jan 14
24°FDec 10Dec 21Dec 27Jan 1Jan 5Jan 11Jan 16Jan 23Feb 3
20°FDec 26Jan 1Jan 6Jan 11Jan 17Jan 21Jan 25Jan 30Feb 7
16°FJan 3Jan 9Jan 12Jan 17Jan 19Jan 24Jan 29Jan 31Feb 8

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°F261252246241237233228223215
32°F290280273267261256252244237
28°F328315306300294288282274264
24°F365351343334328322313307298
20°F365365365365359349340333322
16°F365365365365365365365365343

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
89% of years
20°F or colder
53% of years
16°F or colder
18% 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
1,861
Cooling degree days, base 65°F
2,462
Growing degree days, base 40°F
9,764
Growing degree days, base 45°F
8,021
Growing degree days, base 50°F
6,382
Growing degree days, base 55°F
4,897
Growing degree days, base 60°F
3,585

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January4783108
February3905111
March26323251
April7896469
May9248704
June0438888
July05531,018
August0516981
September1379828
October41162586
November20632290
December3978149

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 11.5 km from Atlantic. 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 USC00311606 (Cedar Is). Public domain.