Banner County climate

Banner County Frost Dates and Growing Season

NOAA 1991-2020 normals for Harrisburg 12WNW, 22.5 km from Banner County, elevation 4550 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Harrisburg 12WNW. 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 20, a growing season of about 117 days.

Median at 36°F
last June 6, first September 12
Median at 32°F
last May 24, first September 20
Median at 28°F
last May 12, first September 29

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 23Jun 18Jun 13Jun 9Jun 6Jun 3May 31May 27May 22
32°FJun 12Jun 5Jun 2May 29May 24May 21May 18May 15May 11
28°FMay 28May 21May 17May 14May 12May 9May 5May 3Apr 29
24°FMay 15May 10May 7May 4May 2Apr 30Apr 26Apr 23Apr 17
20°FMay 8May 2Apr 29Apr 26Apr 22Apr 19Apr 15Apr 11Apr 5
16°FApr 27Apr 22Apr 17Apr 14Apr 10Apr 6Apr 2Mar 29Mar 21

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 28Sep 2Sep 6Sep 9Sep 12Sep 14Sep 17Sep 20Sep 24
32°FSep 6Sep 11Sep 14Sep 17Sep 20Sep 22Sep 25Sep 28Oct 3
28°FSep 13Sep 19Sep 23Sep 26Sep 29Oct 1Oct 4Oct 7Oct 12
24°FSep 23Sep 29Oct 2Oct 5Oct 8Oct 11Oct 14Oct 17Oct 22
20°FOct 4Oct 9Oct 13Oct 16Oct 19Oct 22Oct 24Oct 27Oct 31
16°FOct 14Oct 18Oct 22Oct 24Oct 27Oct 30Nov 1Nov 4Nov 10

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°F1171101051019792888375
32°F13612912412011711310910495
28°F156150145142137133129125118
24°F178171166162157154150144136
20°F199192187182177173168163155
16°F221213207203197193189183175

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
6,936
Cooling degree days, base 65°F
540
Growing degree days, base 40°F
4,380
Growing degree days, base 45°F
3,306
Growing degree days, base 50°F
2,395
Growing degree days, base 55°F
1,639
Growing degree days, base 60°F
1,020

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,16101
February1,00601
March857012
April623044
May35311188
June9482442
July14225675
August28177614
September18645330
October570176
November878011
December1,16701

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 22.5 km from Banner 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 USC00253605 (Harrisburg 12WNW). Public domain.