Halifax County climate

Halifax County Frost Dates and Growing Season

NOAA 1991-2020 normals for S Boston, 9.4 km from Halifax County, elevation 329 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for S Boston. 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 10 and the first fall freeze around October 30, a growing season of about 202 days.

Median at 36°F
last April 23, first October 22
Median at 32°F
last April 10, first October 30
Median at 28°F
last March 29, first November 7

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 10May 4May 1Apr 27Apr 23Apr 20Apr 18Apr 14Apr 10
32°FApr 30Apr 22Apr 17Apr 13Apr 10Apr 7Apr 3Mar 31Mar 25
28°FApr 13Apr 7Apr 3Apr 1Mar 29Mar 26Mar 22Mar 18Mar 12
24°FApr 2Mar 29Mar 24Mar 19Mar 17Mar 14Mar 9Mar 3Feb 25
20°FMar 22Mar 16Mar 11Mar 6Mar 2Feb 27Feb 22Feb 13Feb 4
16°FMar 12Mar 4Feb 27Feb 19Feb 12Feb 6Jan 31Jan 24Jan 15

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 9Oct 13Oct 16Oct 19Oct 22Oct 24Oct 27Oct 30Nov 2
32°FOct 17Oct 22Oct 25Oct 28Oct 30Nov 1Nov 3Nov 6Nov 12
28°FOct 26Oct 30Nov 1Nov 4Nov 7Nov 10Nov 14Nov 18Nov 26
24°FNov 4Nov 9Nov 13Nov 17Nov 21Nov 26Nov 30Dec 3Dec 10
20°FNov 15Nov 22Nov 28Dec 1Dec 6Dec 10Dec 18Dec 25Jan 3
16°FDec 2Dec 9Dec 18Dec 24Dec 31Jan 3Jan 9Jan 15Jan 24

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°F199192188184180176172166159
32°F220214210205202197194188179
28°F249240233228224220216211205
24°F279267260254249244239233225
20°F310301293287281275269261251
16°F347336329323315307301293281

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
96% 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
3,813
Cooling degree days, base 65°F
1,468
Growing degree days, base 40°F
7,129
Growing degree days, base 45°F
5,667
Growing degree days, base 50°F
4,377
Growing degree days, base 55°F
3,251
Growing degree days, base 60°F
2,284

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January818016
February670023
March529489
April25329253
May80113498
June7288731
July0425890
August0375840
September23197624
October21334301
November493284
December728128

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 9.4 km from Halifax County. 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 USC00447925 (S Boston). Public domain.