Lunenburg climate

Lunenburg Frost Dates and Growing Season

NOAA 1991-2020 normals for Keysville 2 S, 20 km from Lunenburg, elevation 625 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Keysville 2 S. 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 8 and the first fall freeze around November 1, a growing season of about 206 days.

Median at 36°F
last April 21, first October 24
Median at 32°F
last April 8, first November 1
Median at 28°F
last March 27, first November 11

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 8May 2Apr 28Apr 24Apr 21Apr 18Apr 16Apr 12Apr 7
32°FApr 25Apr 18Apr 15Apr 11Apr 8Apr 5Apr 2Mar 30Mar 24
28°FApr 10Apr 5Apr 2Mar 31Mar 27Mar 24Mar 20Mar 16Mar 10
24°FMar 30Mar 24Mar 20Mar 16Mar 13Mar 9Mar 5Feb 28Feb 19
20°FMar 17Mar 12Mar 7Mar 3Feb 28Feb 22Feb 15Feb 8Jan 31
16°FMar 8Mar 1Feb 22Feb 14Feb 8Feb 3Jan 30Jan 23Jan 16

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 11Oct 14Oct 18Oct 21Oct 24Oct 26Oct 29Nov 1Nov 4
32°FOct 18Oct 23Oct 27Oct 30Nov 1Nov 3Nov 5Nov 9Nov 13
28°FOct 28Nov 1Nov 5Nov 9Nov 11Nov 14Nov 17Nov 22Nov 30
24°FNov 6Nov 12Nov 16Nov 20Nov 25Nov 29Dec 2Dec 8Dec 18
20°FNov 20Nov 27Dec 2Dec 7Dec 12Dec 18Dec 24Jan 1Jan 9
16°FDec 7Dec 13Dec 23Dec 29Jan 3Jan 7Jan 12Jan 17Jan 25

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°F205198193189185181176171164
32°F226219214210206202197192184
28°F253245240235230226221215208
24°F286277269264259253247240233
20°F320308302295289281275268256
16°F351340333326319312304297286

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
95% 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
4,087
Cooling degree days, base 65°F
1,326
Growing degree days, base 40°F
6,813
Growing degree days, base 45°F
5,382
Growing degree days, base 50°F
4,123
Growing degree days, base 55°F
3,036
Growing degree days, base 60°F
2,111

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January87207
February699019
March570383
April27521227
May10286452
June5252697
July0395860
August1353817
September35180595
October23435281
November529165
December767020

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 20 km from Lunenburg. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00444568 (Keysville 2 S). Public domain.