Mountain Home climate

Mountain Home Frost Dates and Growing Season

NOAA 1991-2020 normals for Mtn Home, 1.9 km from Mountain Home, elevation 3140 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mtn Home. 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 8, a growing season of about 157 days.

Median at 36°F
last May 17, first September 28
Median at 32°F
last May 2, first October 8
Median at 28°F
last April 18, 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°FJun 10Jun 3May 28May 22May 17May 14May 10May 6Apr 30
32°FMay 23May 15May 10May 6May 2Apr 30Apr 26Apr 23Apr 18
28°FMay 8May 1Apr 26Apr 22Apr 18Apr 15Apr 12Apr 7Apr 1
24°FApr 26Apr 17Apr 9Apr 5Apr 2Mar 28Mar 22Mar 16Mar 7
20°FApr 3Mar 27Mar 18Mar 13Mar 9Mar 4Feb 28Feb 23Feb 14
16°FMar 10Mar 3Feb 27Feb 23Feb 19Feb 14Feb 9Feb 2Jan 18

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 11Sep 18Sep 22Sep 25Sep 28Sep 30Oct 3Oct 6Oct 11
32°FSep 25Sep 29Oct 1Oct 5Oct 8Oct 11Oct 14Oct 18Oct 24
28°FOct 4Oct 9Oct 14Oct 17Oct 20Oct 23Oct 26Nov 1Nov 5
24°FOct 14Oct 19Oct 23Oct 27Oct 31Nov 3Nov 7Nov 13Nov 21
20°FOct 21Oct 28Nov 1Nov 6Nov 11Nov 16Nov 21Nov 26Dec 1
16°FOct 31Nov 7Nov 13Nov 18Nov 25Nov 29Dec 3Dec 9Dec 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°F154146141135131125120115106
32°F180172167161157153147140131
28°F208200194189185179174167159
24°F241231224219213207202194185
20°F277267260253246240234227215
16°F315301291285278272265257245

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
5,623
Cooling degree days, base 65°F
1,021
Growing degree days, base 40°F
5,392
Growing degree days, base 45°F
4,188
Growing degree days, base 50°F
3,171
Growing degree days, base 55°F
2,313
Growing degree days, base 60°F
1,604

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,03200
February80501
March681016
April472378
May22342301
June63153541
July5386846
August12334787
September10098451
October4126136
November772013
December1,04600

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 1.9 km from Mountain Home. 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 USC00106174 (Mtn Home). Public domain.