Cambridge climate

Cambridge Frost Dates and Growing Season

NOAA 1991-2020 normals for Ames 5 Se, 6.7 km from Cambridge, elevation 870 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ames 5 Se. 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 26 and the first fall freeze around October 12, a growing season of about 168 days.

Median at 36°F
last May 5, first October 1
Median at 32°F
last April 26, first October 12
Median at 28°F
last April 15, 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 17May 12May 9May 7May 5May 2Apr 30Apr 27Apr 21
32°FMay 8May 4May 1Apr 29Apr 26Apr 23Apr 19Apr 16Apr 11
28°FApr 30Apr 25Apr 22Apr 18Apr 15Apr 13Apr 10Apr 7Apr 2
24°FApr 21Apr 15Apr 12Apr 9Apr 6Apr 4Apr 1Mar 29Mar 21
20°FApr 12Apr 7Apr 3Apr 1Mar 29Mar 24Mar 20Mar 16Mar 11
16°FApr 3Mar 30Mar 24Mar 20Mar 16Mar 13Mar 10Mar 7Mar 2

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 18Sep 23Sep 26Sep 29Oct 1Oct 4Oct 6Oct 10Oct 14
32°FSep 26Oct 1Oct 5Oct 8Oct 12Oct 14Oct 17Oct 20Oct 25
28°FOct 7Oct 13Oct 17Oct 20Oct 22Oct 25Oct 28Oct 31Nov 3
24°FOct 19Oct 24Oct 27Oct 30Nov 1Nov 2Nov 4Nov 8Nov 12
20°FOct 28Nov 1Nov 3Nov 5Nov 8Nov 11Nov 14Nov 18Nov 25
16°FNov 4Nov 8Nov 12Nov 15Nov 18Nov 21Nov 26Dec 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°F167161156152148144140137131
32°F187181176172168164160155147
28°F209201197192189186181176169
24°F229221216213208204200196189
20°F249241236231226222218213205
16°F268260254250245241236231222

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
6,927
Cooling degree days, base 65°F
758
Growing degree days, base 40°F
5,018
Growing degree days, base 45°F
3,927
Growing degree days, base 50°F
2,949
Growing degree days, base 55°F
2,090
Growing degree days, base 60°F
1,357

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,42900
February1,16201
March909019
April511492
May20945318
June28170592
July5260719
August14195646
September12276408
October44710136
November848017
December1,24501

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 6.7 km from Cambridge. 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 USC00130203 (Ames 5 Se). Public domain.