Glenns Ferry climate

Glenns Ferry Frost Dates and Growing Season

NOAA 1991-2020 normals for Glenns Ferry, 2.4 km from Glenns Ferry, elevation 2466 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Glenns Ferry. 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 1 and the first fall freeze around October 3, a growing season of about 154 days.

Median at 36°F
last May 15, first September 21
Median at 32°F
last May 1, first October 3
Median at 28°F
last April 15, first October 16

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 5May 29May 23May 18May 15May 12May 9May 5Apr 30
32°FMay 16May 10May 6May 3May 1Apr 28Apr 25Apr 20Apr 14
28°FMay 2Apr 28Apr 23Apr 19Apr 15Apr 10Apr 6Mar 31Mar 24
24°FApr 18Apr 9Apr 3Mar 30Mar 25Mar 20Mar 14Mar 10Mar 3
20°FMar 27Mar 17Mar 11Mar 6Mar 3Feb 28Feb 25Feb 18Feb 7
16°FMar 5Feb 28Feb 24Feb 18Feb 13Feb 7Feb 2Jan 25Jan 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 5Sep 10Sep 15Sep 18Sep 21Sep 24Sep 28Oct 2Oct 7
32°FSep 16Sep 22Sep 26Sep 30Oct 3Oct 6Oct 10Oct 14Oct 19
28°FSep 29Oct 4Oct 8Oct 12Oct 16Oct 18Oct 23Oct 26Nov 1
24°FOct 9Oct 17Oct 22Oct 25Oct 29Nov 1Nov 4Nov 9Nov 18
20°FOct 24Oct 30Nov 2Nov 6Nov 10Nov 14Nov 19Nov 25Dec 3
16°FNov 2Nov 10Nov 15Nov 20Nov 25Nov 29Dec 4Dec 11Dec 21

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°F150142138133128124117111102
32°F176168164159154149146140131
28°F209202196190184179174167159
24°F247238229222217211205198188
20°F283271264257252246240233220
16°F326310299291283277271263254

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
4,934
Cooling degree days, base 65°F
1,173
Growing degree days, base 40°F
5,980
Growing degree days, base 45°F
4,662
Growing degree days, base 50°F
3,542
Growing degree days, base 55°F
2,594
Growing degree days, base 60°F
1,811

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January95200
February74502
March583036
April3756133
May15562377
June38196608
July2431894
August6361820
September74110488
October3597164
November692018
December95501

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 2.4 km from Glenns Ferry. 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 USC00103631 (Glenns Ferry). Public domain.