Princeton climate

Princeton Frost Dates and Growing Season

NOAA 1991-2020 normals for Princeton, 0.4 km from Princeton, elevation 980 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Princeton. 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 25 and the first fall freeze around October 15, a growing season of about 174 days.

Median at 36°F
last May 5, first October 5
Median at 32°F
last April 25, first October 15
Median at 28°F
last April 14, first October 26

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 18May 13May 9May 7May 5May 2Apr 30Apr 26Apr 20
32°FMay 8May 4May 1Apr 28Apr 25Apr 21Apr 18Apr 15Apr 11
28°FApr 28Apr 23Apr 20Apr 16Apr 14Apr 10Apr 7Apr 4Mar 31
24°FApr 16Apr 11Apr 8Apr 5Apr 3Mar 31Mar 28Mar 24Mar 17
20°FApr 8Apr 3Mar 31Mar 27Mar 23Mar 20Mar 16Mar 11Mar 5
16°FMar 31Mar 25Mar 20Mar 16Mar 13Mar 9Mar 6Mar 2Feb 25

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 21Sep 26Sep 29Oct 2Oct 5Oct 8Oct 11Oct 14Oct 19
32°FSep 30Oct 5Oct 9Oct 13Oct 15Oct 18Oct 21Oct 25Oct 29
28°FOct 11Oct 17Oct 21Oct 23Oct 26Oct 29Oct 31Nov 2Nov 8
24°FOct 21Oct 26Oct 30Nov 1Nov 3Nov 6Nov 9Nov 13Nov 18
20°FOct 31Nov 3Nov 6Nov 9Nov 12Nov 15Nov 19Nov 24Dec 1
16°FNov 6Nov 11Nov 15Nov 19Nov 22Nov 26Nov 30Dec 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°F172166161157153149144140133
32°F194186181177174169165159152
28°F213207202198195191186181172
24°F235228223218214210206201196
20°F256247242237232228224219212
16°F276268261256252247241235228

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
6,012
Cooling degree days, base 65°F
991
Growing degree days, base 40°F
5,619
Growing degree days, base 45°F
4,435
Growing degree days, base 50°F
3,378
Growing degree days, base 55°F
2,452
Growing degree days, base 60°F
1,652

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26600
February1,02204
March774241
April4297134
May17456358
June20204634
July2329792
August6272731
September95105464
October37015185
November743033
December1,11302

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 0.4 km from Princeton. 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 USC00236866 (Princeton). Public domain.