Harper County climate

Harper County Frost Dates and Growing Season

NOAA 1991-2020 normals for Buffalo 2 Ssw, 2.7 km from Harper County, elevation 1931 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Buffalo 2 Ssw. 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 April 17 and the first fall freeze around October 23, a growing season of about 187 days.

Median at 36°F
last April 27, first October 15
Median at 32°F
last April 17, first October 23
Median at 28°F
last April 7, first November 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°FMay 8May 4May 1Apr 29Apr 27Apr 24Apr 21Apr 17Apr 12
32°FApr 30Apr 27Apr 23Apr 20Apr 17Apr 14Apr 10Apr 7Apr 3
28°FApr 22Apr 17Apr 13Apr 10Apr 7Apr 4Mar 31Mar 28Mar 22
24°FApr 12Apr 7Apr 3Mar 31Mar 29Mar 25Mar 21Mar 15Mar 7
20°FApr 4Mar 31Mar 27Mar 21Mar 17Mar 12Mar 8Mar 3Feb 27
16°FMar 27Mar 20Mar 14Mar 9Mar 5Mar 1Feb 26Feb 20Feb 12

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 30Oct 5Oct 9Oct 12Oct 15Oct 17Oct 20Oct 23Oct 27
32°FOct 8Oct 14Oct 18Oct 21Oct 23Oct 26Oct 29Nov 1Nov 4
28°FOct 18Oct 22Oct 26Oct 30Nov 1Nov 4Nov 7Nov 10Nov 15
24°FOct 26Oct 31Nov 3Nov 6Nov 9Nov 12Nov 15Nov 19Nov 25
20°FNov 1Nov 5Nov 10Nov 14Nov 17Nov 21Nov 25Nov 29Dec 4
16°FNov 7Nov 14Nov 19Nov 24Nov 27Dec 1Dec 4Dec 10Dec 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°F188181177173170166163158150
32°F208201195191187183179174169
28°F231222217213208203199194187
24°F250243237233227223219213205
20°F271263256251246241237232222
16°F293285277271265260254247238

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
4,372
Cooling degree days, base 65°F
1,827
Growing degree days, base 40°F
7,264
Growing degree days, base 45°F
5,886
Growing degree days, base 50°F
4,661
Growing degree days, base 55°F
3,578
Growing degree days, base 60°F
2,637

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January93905
February742019
March564389
April28732243
May82135521
June4366811
July05381,003
August1466930
September30240660
October24245302
November570372
December91108

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 2.7 km from Harper County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00341243 (Buffalo 2 Ssw). Public domain.