Suffolk climate

Suffolk Frost Dates and Growing Season

NOAA 1991-2020 normals for Suffolk Lake Kilby, 1.5 km from Suffolk, elevation 22 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Suffolk Lake Kilby. 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 27 and the first fall freeze around November 15, a growing season of about 233 days.

Median at 36°F
last April 6, first November 3
Median at 32°F
last March 27, first November 15
Median at 28°F
last March 15, first December 1

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 20Apr 15Apr 12Apr 9Apr 6Apr 4Apr 1Mar 29Mar 23
32°FApr 9Apr 5Apr 1Mar 30Mar 27Mar 23Mar 20Mar 16Mar 10
28°FMar 30Mar 25Mar 21Mar 17Mar 15Mar 11Mar 6Mar 2Feb 24
24°FMar 19Mar 14Mar 10Mar 5Feb 28Feb 25Feb 19Feb 11Feb 2
20°FMar 8Mar 2Feb 25Feb 18Feb 11Feb 6Feb 1Jan 25Jan 16
16°FFeb 24Feb 14Feb 5Jan 31Jan 29Jan 24Jan 18Jan 11Jan 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°FOct 23Oct 27Oct 30Nov 1Nov 3Nov 5Nov 7Nov 11Nov 16
32°FNov 2Nov 6Nov 9Nov 12Nov 15Nov 18Nov 22Nov 27Dec 1
28°FNov 11Nov 17Nov 21Nov 26Dec 1Dec 3Dec 6Dec 12Dec 22
24°FNov 28Dec 2Dec 7Dec 12Dec 18Dec 24Dec 29Jan 3Jan 12
20°FDec 10Dec 19Dec 26Dec 31Jan 3Jan 7Jan 13Jan 18Jan 29
16°FDec 23Dec 31Jan 3Jan 7Jan 12Jan 17Jan 22Jan 27Feb 2

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°F228221217214210207203199193
32°F255248242237233229224220214
28°F288276270264259254249243235
24°F320310302297291285279271262
20°F352340333326320313306301293
16°F365365365354346339334327315

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
94% of years
16°F or colder
69% 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
3,465
Cooling degree days, base 65°F
1,462
Growing degree days, base 40°F
7,392
Growing degree days, base 45°F
5,872
Growing degree days, base 50°F
4,525
Growing degree days, base 55°F
3,336
Growing degree days, base 60°F
2,315

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January769026
February626032
March4953104
April22533277
May69112509
June5283727
July0411876
August0367832
September15204639
October16743349
November4344111
December660144

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 1.5 km from Suffolk. 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 USC00448192 (Suffolk Lake Kilby). Public domain.