Star climate

Star Frost Dates and Growing Season

NOAA 1991-2020 normals for Nampa Sugar Factory, 11.8 km from Star, elevation 2470 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Nampa Sugar Factory. 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 29 and the first fall freeze around October 13, a growing season of about 164 days.

Median at 36°F
last May 16, first September 30
Median at 32°F
last April 29, first October 13
Median at 28°F
last April 11, first October 25

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 6May 31May 24May 20May 16May 13May 10May 6May 1
32°FMay 18May 9May 5May 1Apr 29Apr 27Apr 23Apr 20Apr 15
28°FMay 1Apr 25Apr 20Apr 16Apr 11Apr 8Apr 4Mar 31Mar 25
24°FApr 12Apr 6Apr 1Mar 28Mar 22Mar 17Mar 12Mar 8Mar 2
20°FMar 26Mar 13Mar 9Mar 4Feb 28Feb 26Feb 21Feb 16Feb 8
16°FMar 3Feb 25Feb 21Feb 16Feb 11Feb 6Jan 31Jan 22Jan 7

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 15Sep 20Sep 24Sep 27Sep 30Oct 2Oct 5Oct 8Oct 14
32°FSep 29Oct 3Oct 6Oct 9Oct 13Oct 16Oct 19Oct 22Oct 28
28°FOct 9Oct 15Oct 18Oct 22Oct 25Oct 28Nov 1Nov 4Nov 10
24°FOct 22Oct 27Nov 1Nov 3Nov 6Nov 10Nov 14Nov 19Nov 24
20°FOct 31Nov 6Nov 11Nov 15Nov 19Nov 23Nov 26Nov 30Dec 5
16°FNov 9Nov 16Nov 23Nov 27Dec 1Dec 4Dec 8Dec 14Dec 24

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°F155148143139134129125119111
32°F186179172168164160155150142
28°F220211204199195190184178169
24°F254245238233227222215209201
20°F291280273268261256248241231
16°F333319307300294289280273264

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
99% 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
5,549
Cooling degree days, base 65°F
825
Growing degree days, base 40°F
5,234
Growing degree days, base 45°F
4,001
Growing degree days, base 50°F
2,956
Growing degree days, base 55°F
2,090
Growing degree days, base 60°F
1,385

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04600
February79501
March636021
April442285
May21931289
June65122507
July6325784
August10275730
September10668415
October4203115
November76308
December1,04100

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 11.8 km from Star. 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 USC00106305 (Nampa Sugar Factory). Public domain.