Mount Morris climate

Mount Morris Frost Dates and Growing Season

NOAA 1991-2020 normals for Hancock Exp Farm, 27.5 km from Mount Morris, elevation 1092 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hancock Exp Farm. 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 10 and the first fall freeze around October 3, a growing season of about 146 days.

Median at 36°F
last May 20, first September 24
Median at 32°F
last May 10, first October 3
Median at 28°F
last April 30, first October 14

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

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 12Sep 17Sep 19Sep 22Sep 24Sep 27Sep 29Oct 3Oct 6
32°FSep 20Sep 24Sep 27Oct 1Oct 3Oct 6Oct 8Oct 12Oct 16
28°FSep 29Oct 4Oct 7Oct 11Oct 14Oct 17Oct 20Oct 24Oct 29
24°FOct 10Oct 15Oct 20Oct 23Oct 26Oct 29Nov 1Nov 4Nov 9
20°FOct 25Oct 30Nov 1Nov 3Nov 6Nov 8Nov 11Nov 15Nov 20
16°FNov 2Nov 6Nov 9Nov 12Nov 14Nov 17Nov 20Nov 23Nov 27

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°F146139135130126123119115108
32°F165158154149146142137133126
28°F188181175170166162159153147
24°F212205200195190186182176168
20°F233225220217213209205200193
16°F250244238234230226222218210

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
7,864
Cooling degree days, base 65°F
502
Growing degree days, base 40°F
4,293
Growing degree days, base 45°F
3,291
Growing degree days, base 50°F
2,407
Growing degree days, base 55°F
1,640
Growing degree days, base 60°F
997

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,52200
February1,27000
March1,047111
April632252
May28930243
June67106489
July19178625
August33135567
September18246327
October539486
November92708
December1,33800

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 27.5 km from Mount Morris. 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 USC00473405 (Hancock Exp Farm). Public domain.