Killdeer climate

Killdeer Frost Dates and Growing Season

NOAA 1991-2020 normals for Killdeer, 0.5 km from Killdeer, elevation 2310 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Killdeer. 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 21 and the first fall freeze around September 23, a growing season of about 124 days.

Median at 36°F
last June 1, first September 13
Median at 32°F
last May 21, first September 23
Median at 28°F
last May 10, first October 1

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 10Jun 6Jun 3Jun 1May 29May 26May 24May 20
32°FJun 5May 31May 27May 24May 21May 18May 15May 13May 9
28°FMay 24May 19May 16May 13May 10May 7May 5May 2Apr 29
24°FMay 13May 8May 5May 2Apr 30Apr 28Apr 24Apr 20Apr 15
20°FMay 2Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 10Apr 6
16°FApr 25Apr 21Apr 17Apr 13Apr 10Apr 7Apr 4Apr 1Mar 24

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 29Sep 3Sep 7Sep 10Sep 13Sep 16Sep 19Sep 22Sep 25
32°FSep 8Sep 13Sep 18Sep 20Sep 23Sep 25Sep 27Oct 1Oct 5
28°FSep 19Sep 23Sep 26Sep 28Oct 1Oct 4Oct 6Oct 10Oct 14
24°FSep 26Oct 1Oct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 24
20°FOct 5Oct 10Oct 14Oct 16Oct 19Oct 22Oct 25Oct 29Nov 3
16°FOct 12Oct 18Oct 22Oct 25Oct 29Nov 1Nov 4Nov 7Nov 12

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°F11911411010710399948981
32°F141136132128124120117111105
28°F161155151147143140135131124
24°F182176170167164160155150142
20°F203195190186182178174169163
16°F221214209204200196192187180

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
8,603
Cooling degree days, base 65°F
373
Growing degree days, base 40°F
3,789
Growing degree days, base 45°F
2,846
Growing degree days, base 50°F
2,024
Growing degree days, base 55°F
1,333
Growing degree days, base 60°F
776

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,54100
February1,29400
March1,09003
April703130
May3797159
June12644371
July30150584
August49140557
September23931269
October668148
November1,06103
December1,42400

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 0.5 km from Killdeer. 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 USC00324722 (Killdeer). Public domain.