Cortland climate

Cortland Frost Dates and Growing Season

NOAA 1991-2020 normals for De Kalb, 7.3 km from Cortland, elevation 873 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for De Kalb. 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 24 and the first fall freeze around October 18, a growing season of about 177 days.

Median at 36°F
last May 4, first October 7
Median at 32°F
last April 24, first October 18
Median at 28°F
last April 13, first October 28

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 22May 15May 11May 7May 4May 1Apr 29Apr 25Apr 20
32°FMay 10May 4Apr 30Apr 27Apr 24Apr 21Apr 17Apr 14Apr 9
28°FApr 29Apr 24Apr 20Apr 16Apr 13Apr 9Apr 6Apr 3Mar 30
24°FApr 16Apr 10Apr 6Apr 4Apr 2Mar 31Mar 27Mar 22Mar 17
20°FApr 4Apr 1Mar 29Mar 25Mar 22Mar 19Mar 15Mar 12Mar 7
16°FMar 29Mar 24Mar 20Mar 17Mar 13Mar 10Mar 7Mar 3Feb 26

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 25Sep 29Oct 1Oct 5Oct 7Oct 10Oct 13Oct 17Oct 21
32°FOct 4Oct 9Oct 13Oct 15Oct 18Oct 21Oct 23Oct 26Oct 31
28°FOct 14Oct 19Oct 22Oct 25Oct 28Oct 31Nov 2Nov 7Nov 12
24°FOct 24Oct 30Nov 1Nov 5Nov 8Nov 11Nov 15Nov 19Nov 24
20°FNov 3Nov 8Nov 12Nov 15Nov 18Nov 21Nov 24Nov 28Dec 2
16°FNov 11Nov 16Nov 20Nov 23Nov 26Nov 29Dec 2Dec 6Dec 13

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°F175168164160156151147142135
32°F197190185181177172167163155
28°F217211206202198195190184178
24°F239232227223219215210206200
20°F262253248243238234230226218
16°F279271266261257253248242235

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
6,745
Cooling degree days, base 65°F
790
Growing degree days, base 40°F
5,061
Growing degree days, base 45°F
3,965
Growing degree days, base 50°F
2,987
Growing degree days, base 55°F
2,128
Growing degree days, base 60°F
1,393

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,37600
February1,13301
March903120
April515489
May21551318
June34175591
July5259719
August12206659
September11485426
October4289144
November812019
December1,19802

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 7.3 km from Cortland. 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 USC00112223 (De Kalb). Public domain.