Randolph climate

Randolph Frost Dates and Growing Season

NOAA 1991-2020 normals for Town Of Westford, 12.5 km from Randolph, elevation 879 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Town Of Westford. 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 1 and the first fall freeze around October 11, a growing season of about 163 days.

Median at 36°F
last May 11, first October 1
Median at 32°F
last May 1, first October 11
Median at 28°F
last April 19, first October 22

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 18May 14May 11May 8May 5May 2Apr 29
32°FMay 16May 10May 6May 3May 1Apr 29Apr 25Apr 22Apr 16
28°FMay 3Apr 30Apr 25Apr 22Apr 19Apr 16Apr 14Apr 10Apr 6
24°FApr 21Apr 17Apr 14Apr 11Apr 9Apr 6Apr 4Apr 2Mar 28
20°FApr 13Apr 8Apr 6Apr 3Apr 1Mar 30Mar 26Mar 22Mar 16
16°FApr 5Apr 1Mar 30Mar 26Mar 22Mar 19Mar 16Mar 12Mar 7

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

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°F160154150146143139136131123
32°F182174170166163159155150144
28°F204198193188184179175170164
24°F225219214210207203200195188
20°F247239234230226223219213206
16°F264257252248244239234229222

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
7,601
Cooling degree days, base 65°F
513
Growing degree days, base 40°F
4,425
Growing degree days, base 45°F
3,398
Growing degree days, base 50°F
2,497
Growing degree days, base 55°F
1,708
Growing degree days, base 60°F
1,042

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,49400
February1,25600
March1,030113
April610152
May26828254
June48108510
July12184637
August22141584
September16347343
October509494
November89109
December1,29900

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 12.5 km from Randolph. 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 USC00478540 (Town Of Westford). Public domain.