Logan County climate

Logan County Frost Dates and Growing Season

NOAA 1991-2020 normals for Napoleon, 23 km from Logan County, elevation 1980 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Napoleon. 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 13 and the first fall freeze around September 28, a growing season of about 136 days.

Median at 36°F
last May 23, first September 19
Median at 32°F
last May 13, first September 28
Median at 28°F
last May 4, first October 6

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 4May 31May 28May 25May 23May 20May 17May 15May 10
32°FMay 26May 22May 18May 16May 13May 11May 8May 5May 1
28°FMay 16May 13May 9May 6May 4May 1Apr 30Apr 25Apr 20
24°FMay 9May 4May 1Apr 28Apr 24Apr 21Apr 18Apr 14Apr 10
20°FMay 1Apr 25Apr 21Apr 18Apr 16Apr 13Apr 10Apr 6Apr 1
16°FApr 21Apr 17Apr 13Apr 10Apr 7Apr 4Apr 1Mar 29Mar 22

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 7Sep 11Sep 14Sep 17Sep 19Sep 22Sep 24Sep 27Oct 1
32°FSep 15Sep 19Sep 23Sep 26Sep 28Oct 1Oct 3Oct 6Oct 11
28°FSep 24Sep 29Oct 1Oct 4Oct 6Oct 9Oct 12Oct 15Oct 20
24°FOct 3Oct 6Oct 10Oct 13Oct 16Oct 19Oct 22Oct 25Oct 29
20°FOct 11Oct 16Oct 20Oct 22Oct 25Oct 28Oct 31Nov 3Nov 8
16°FOct 20Oct 26Oct 29Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17

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°F135130125123119115111106100
32°F153147143139136133129125118
28°F173167162158153150146142137
24°F192186182177173169165160152
20°F213205201196192188184178170
16°F232224218213209206200195188

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
9,065
Cooling degree days, base 65°F
441
Growing degree days, base 40°F
3,906
Growing degree days, base 45°F
2,979
Growing degree days, base 50°F
2,158
Growing degree days, base 55°F
1,457
Growing degree days, base 60°F
878

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,70000
February1,42200
March1,19203
April725030
May36014188
June9972425
July27172609
August46140560
September23340284
October654257
November1,09502
December1,51100

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 23 km from Logan 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 USC00326255 (Napoleon). Public domain.