College climate

College Frost Dates and Growing Season

NOAA 1991-2020 normals for College Obsy, 2.2 km from College, elevation 597 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for College Obsy. 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 18 and the first fall freeze around September 6, a growing season of about 111 days.

Median at 36°F
last May 31, first August 26
Median at 32°F
last May 18, first September 6
Median at 28°F
last May 7, first September 20

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°FJun 16Jun 8Jun 4Jun 1May 31May 28May 26May 21May 17
32°FJun 1May 28May 24May 21May 18May 15May 13May 10May 7
28°FMay 22May 15May 12May 9May 7May 5May 3Apr 30Apr 26
24°FMay 11May 7May 4May 2Apr 30Apr 27Apr 24Apr 20Apr 15
20°FMay 4May 1Apr 28Apr 25Apr 22Apr 19Apr 16Apr 12Apr 9
16°FApr 30Apr 25Apr 22Apr 18Apr 16Apr 13Apr 10Apr 8Apr 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°FAug 11Aug 16Aug 20Aug 23Aug 26Aug 29Sep 1Sep 3Sep 7
32°FAug 24Aug 29Sep 1Sep 3Sep 6Sep 10Sep 13Sep 17Sep 20
28°FSep 5Sep 10Sep 14Sep 17Sep 20Sep 22Sep 25Sep 28Oct 1
24°FSep 15Sep 20Sep 24Sep 27Sep 30Oct 2Oct 5Oct 8Oct 12
20°FSep 24Sep 29Oct 1Oct 4Oct 7Oct 9Oct 12Oct 14Oct 18
16°FSep 30Oct 5Oct 8Oct 11Oct 13Oct 16Oct 19Oct 22Oct 25

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°F1059994908784797465
32°F1301241191151111071039790
28°F152145141137133129125120114
24°F170164160156152149145139132
20°F184179175171167163160154148
16°F195190186182179176172168162

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
13,331
Cooling degree days, base 65°F
47
Growing degree days, base 40°F
2,212
Growing degree days, base 45°F
1,500
Growing degree days, base 50°F
906
Growing degree days, base 55°F
462
Growing degree days, base 60°F
181

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January2,15900
February1,72600
March1,63800
April96504
May510171
June19919277
July14323348
August3045183
September626024
October1,21801
November1,78200
December2,06200

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 2.2 km from College. 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 USC00502107 (College Obsy). Public domain.