Traill County climate

Traill County Frost Dates and Growing Season

NOAA 1991-2020 normals for Hillsboro 3 N, 7.4 km from Traill County, elevation 910 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hillsboro 3 N. 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 2 and the first fall freeze around October 9, a growing season of about 158 days.

Median at 36°F
last May 11, first September 30
Median at 32°F
last May 2, first October 9
Median at 28°F
last April 23, first October 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°FMay 24May 20May 17May 14May 11May 8May 5May 2Apr 29
32°FMay 17May 12May 8May 5May 2Apr 30Apr 27Apr 23Apr 15
28°FMay 8May 2Apr 29Apr 26Apr 23Apr 19Apr 15Apr 11Apr 6
24°FApr 29Apr 23Apr 18Apr 15Apr 11Apr 8Apr 6Apr 3Mar 31
20°FApr 18Apr 13Apr 9Apr 6Apr 4Apr 2Mar 31Mar 26Mar 19
16°FApr 10Apr 6Apr 3Apr 1Mar 30Mar 25Mar 22Mar 17Mar 13

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 15Sep 21Sep 25Sep 27Sep 30Oct 2Oct 5Oct 8Oct 13
32°FSep 25Sep 30Oct 3Oct 6Oct 9Oct 13Oct 16Oct 20Oct 25
28°FOct 2Oct 8Oct 13Oct 17Oct 20Oct 23Oct 27Oct 31Nov 4
24°FOct 12Oct 19Oct 23Oct 27Oct 30Nov 1Nov 4Nov 8Nov 11
20°FOct 23Oct 29Nov 1Nov 3Nov 6Nov 8Nov 11Nov 14Nov 19
16°FOct 31Nov 4Nov 7Nov 10Nov 12Nov 15Nov 18Nov 21Nov 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°F157150147143140136132128122
32°F179172166162158154150146139
28°F201193187182177173168162155
24°F218211206202197192188183176
20°F233226222218214210206201193
16°F247240235231227223220215209

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
8,681
Cooling degree days, base 65°F
573
Growing degree days, base 40°F
4,299
Growing degree days, base 45°F
3,329
Growing degree days, base 50°F
2,465
Growing degree days, base 55°F
1,711
Growing degree days, base 60°F
1,074

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,72200
February1,44600
March1,15604
April650143
May28125248
June59123515
July16208657
August28161598
September18651329
October593469
November1,04203
December1,50200

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 7.4 km from Traill County. 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 USC00324203 (Hillsboro 3 N). Public domain.