Cambridge climate

Cambridge Frost Dates and Growing Season

NOAA 1991-2020 normals for Cambridge, 2 km from Cambridge, elevation 965 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cambridge. 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 2 and the first fall freeze around October 4, a growing season of about 153 days.

Median at 36°F
last May 13, first September 26
Median at 32°F
last May 2, first October 4
Median at 28°F
last April 21, first October 15

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 28May 24May 20May 16May 13May 10May 6May 3Apr 29
32°FMay 20May 13May 9May 5May 2Apr 30Apr 27Apr 22Apr 17
28°FMay 6Apr 30Apr 28Apr 24Apr 21Apr 18Apr 15Apr 11Apr 6
24°FApr 25Apr 20Apr 17Apr 13Apr 10Apr 7Apr 5Apr 2Mar 29
20°FApr 17Apr 12Apr 8Apr 5Apr 3Apr 1Mar 29Mar 24Mar 19
16°FApr 11Apr 5Apr 2Mar 31Mar 28Mar 24Mar 21Mar 17Mar 13

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

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°F155147143138133130126121114
32°F175167161157153149144138131
28°F199190185180175171166160152
24°F220213209204200196192186177
20°F238231226221217214210205198
16°F251244240235231228223218211

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
8,124
Cooling degree days, base 65°F
546
Growing degree days, base 40°F
4,382
Growing degree days, base 45°F
3,377
Growing degree days, base 50°F
2,484
Growing degree days, base 55°F
1,707
Growing degree days, base 60°F
1,059

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,62000
February1,33800
March1,08007
April609153
May26727252
June56115509
July12205659
August25147587
September18348327
October547381
November96309
December1,42400

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 2 km from Cambridge. 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 USC00211227 (Cambridge). Public domain.