Cambridge climate

Cambridge Frost Dates and Growing Season

NOAA 1991-2020 normals for Cambridge, 1.9 km from Cambridge, elevation 2239 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 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 30
Median at 32°F
last May 3, first October 5
Median at 28°F
last April 23, 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 26May 21May 18May 15May 13May 10May 8May 5May 2
32°FMay 15May 11May 8May 5May 3May 1Apr 29Apr 25Apr 20
28°FMay 7May 2Apr 30Apr 26Apr 23Apr 20Apr 18Apr 14Apr 9
24°FApr 28Apr 23Apr 19Apr 17Apr 13Apr 10Apr 7Apr 4Mar 31
20°FApr 17Apr 12Apr 8Apr 5Apr 2Mar 31Mar 27Mar 22Mar 16
16°FApr 8Apr 4Mar 31Mar 28Mar 23Mar 20Mar 15Mar 11Mar 5

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 27Sep 30Oct 1Oct 3Oct 6Oct 10
32°FSep 24Sep 29Oct 1Oct 3Oct 5Oct 8Oct 11Oct 14Oct 18
28°FOct 3Oct 7Oct 11Oct 14Oct 16Oct 18Oct 20Oct 23Oct 26
24°FOct 13Oct 17Oct 20Oct 22Oct 24Oct 26Oct 29Nov 1Nov 4
20°FOct 19Oct 23Oct 27Oct 30Nov 1Nov 3Nov 5Nov 9Nov 14
16°FOct 26Oct 31Nov 3Nov 5Nov 8Nov 11Nov 15Nov 19Nov 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°F156149145142138135131126120
32°F173167163159156152149145137
28°F194189183179175172168164157
24°F215208204200196192189183176
20°F234226221216213209204199193
16°F254246240235230226221215208

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
6,074
Cooling degree days, base 65°F
1,032
Growing degree days, base 40°F
5,502
Growing degree days, base 45°F
4,332
Growing degree days, base 50°F
3,306
Growing degree days, base 55°F
2,416
Growing degree days, base 60°F
1,659

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,17800
February97703
March763029
April4645108
May20351332
June27214638
July3354817
August7286744
September102112466
October4218151
November789019
December1,14100

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 1.9 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 USC00251415 (Cambridge). Public domain.