Minidoka County climate

Minidoka County Frost Dates and Growing Season

NOAA 1991-2020 normals for Minidoka Dam, 22.6 km from Minidoka County, elevation 4164 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Minidoka Dam. 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 16 and the first fall freeze around October 1, a growing season of about 136 days.

Median at 36°F
last June 3, first September 15
Median at 32°F
last May 16, first October 1
Median at 28°F
last May 2, first October 15

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 22Jun 15Jun 10Jun 6Jun 3May 31May 26May 22May 16
32°FJun 5May 30May 24May 20May 16May 13May 9May 5Apr 30
28°FMay 19May 12May 8May 4May 2Apr 29Apr 25Apr 22Apr 16
24°FMay 3Apr 29Apr 24Apr 20Apr 17Apr 13Apr 9Apr 4Mar 29
20°FApr 17Apr 11Apr 6Apr 2Mar 30Mar 25Mar 18Mar 13Mar 6
16°FMar 31Mar 22Mar 15Mar 10Mar 7Mar 3Feb 28Feb 22Feb 14

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 1Sep 5Sep 8Sep 12Sep 15Sep 18Sep 21Sep 24Oct 1
32°FSep 13Sep 20Sep 24Sep 28Oct 1Oct 3Oct 6Oct 11Oct 16
28°FSep 30Oct 4Oct 7Oct 11Oct 15Oct 17Oct 20Oct 24Oct 30
24°FOct 10Oct 16Oct 19Oct 23Oct 26Oct 28Oct 31Nov 3Nov 8
20°FOct 16Oct 21Oct 26Oct 30Nov 1Nov 5Nov 8Nov 13Nov 20
16°FOct 21Oct 28Nov 1Nov 6Nov 10Nov 15Nov 20Nov 25Dec 1

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°F12611911310810399948776
32°F159152146141136130125118108
28°F183176172168164159154147140
24°F215206200195190186180175167
20°F247236228222217212207200192
16°F274265258252247241234225215

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
6,483
Cooling degree days, base 65°F
541
Growing degree days, base 40°F
4,469
Growing degree days, base 45°F
3,359
Growing degree days, base 50°F
2,425
Growing degree days, base 55°F
1,647
Growing degree days, base 60°F
1,018

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,16100
February92800
March76609
April558146
May30613207
June11469408
July15222673
August24188629
September16046346
October486298
November82509
December1,14200

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 22.6 km from Minidoka 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 USC00105980 (Minidoka Dam). Public domain.