Lyndeborough climate

Lyndeborough Frost Dates and Growing Season

NOAA 1991-2020 normals for Milford, 12.2 km from Lyndeborough, elevation 320 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Milford. 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 May 3 and the first fall freeze around October 5, a growing season of about 156 days.

Median at 36°F
last May 13, first September 28
Median at 32°F
last May 3, first October 5
Median at 28°F
last April 20, first October 16

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

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°F153147143140136133130126121
32°F173167163160156152149144138
28°F198191187183179175171166161
24°F222217212208204201197192186
20°F247239234230226222219214207
16°F270262257252248244239235226

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
6,825
Cooling degree days, base 65°F
546
Growing degree days, base 40°F
4,492
Growing degree days, base 45°F
3,421
Growing degree days, base 50°F
2,495
Growing degree days, base 55°F
1,703
Growing degree days, base 60°F
1,050

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27901
February1,10500
March96003
April564357
May26620234
June71105485
July8217674
August20157601
September15142346
October497380
November791012
December1,11401

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 12.2 km from Lyndeborough. 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 USC00275412 (Milford). Public domain.