Blackduck climate

Blackduck Frost Dates and Growing Season

NOAA 1991-2020 normals for Blackduck, 7.2 km from Blackduck, elevation 1340 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Blackduck. 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 24 and the first fall freeze around September 17, a growing season of about 115 days.

Median at 36°F
last June 4, first September 6
Median at 32°F
last May 24, first September 17
Median at 28°F
last May 13, first September 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°FJun 24Jun 16Jun 12Jun 7Jun 4Jun 2May 30May 27May 23
32°FJun 6Jun 1May 29May 26May 24May 21May 18May 14May 9
28°FMay 27May 22May 18May 15May 13May 10May 7May 3Apr 30
24°FMay 16May 12May 6May 4May 2Apr 30Apr 27Apr 24Apr 20
20°FMay 5May 1Apr 28Apr 25Apr 23Apr 20Apr 17Apr 13Apr 8
16°FApr 26Apr 22Apr 19Apr 16Apr 13Apr 11Apr 8Apr 5Apr 1

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 19Aug 26Aug 31Sep 3Sep 6Sep 9Sep 13Sep 16Sep 21
32°FSep 1Sep 6Sep 10Sep 14Sep 17Sep 20Sep 23Sep 27Oct 1
28°FSep 10Sep 15Sep 20Sep 25Sep 28Oct 1Oct 4Oct 8Oct 13
24°FSep 21Sep 27Oct 1Oct 5Oct 9Oct 12Oct 15Oct 19Oct 25
20°FOct 1Oct 9Oct 14Oct 19Oct 22Oct 26Oct 30Nov 2Nov 7
16°FOct 13Oct 22Oct 28Oct 31Nov 2Nov 5Nov 8Nov 12Nov 16

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°F113106101969286817666
32°F13612912411911511110610091
28°F158150146141137132128122114
24°F179173168163159155151145137
20°F203196190186182177173167159
16°F220214210207203199194189182

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
10,094
Cooling degree days, base 65°F
195
Growing degree days, base 40°F
3,258
Growing degree days, base 45°F
2,386
Growing degree days, base 50°F
1,635
Growing degree days, base 55°F
1,006
Growing degree days, base 60°F
516

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,87100
February1,55100
March1,29601
April806015
May4297133
June14433344
July5987493
August9357430
September31510187
October723032
November1,16600
December1,64300

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 7.2 km from Blackduck. 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 USC00210809 (Blackduck). Public domain.