Fertile climate

Fertile Frost Dates and Growing Season

NOAA 1991-2020 normals for Ada, 31.8 km from Fertile, elevation 907 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ada. 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 11 and the first fall freeze around September 27, a growing season of about 137 days.

Median at 36°F
last May 22, first September 17
Median at 32°F
last May 11, first September 27
Median at 28°F
last May 2, first October 6

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 3May 31May 27May 25May 22May 19May 16May 13May 9
32°FMay 25May 20May 17May 14May 11May 8May 6May 3Apr 30
28°FMay 18May 13May 8May 5May 2Apr 30Apr 27Apr 24Apr 18
24°FMay 7May 2Apr 29Apr 25Apr 22Apr 19Apr 16Apr 12Apr 7
20°FApr 27Apr 21Apr 18Apr 15Apr 12Apr 9Apr 6Apr 4Mar 31
16°FApr 18Apr 13Apr 9Apr 7Apr 4Apr 3Apr 1Mar 27Mar 22

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 2Sep 8Sep 12Sep 15Sep 17Sep 20Sep 22Sep 25Sep 29
32°FSep 14Sep 19Sep 22Sep 25Sep 27Sep 30Oct 2Oct 5Oct 9
28°FSep 23Sep 27Oct 1Oct 3Oct 6Oct 9Oct 13Oct 17Oct 21
24°FOct 1Oct 6Oct 10Oct 14Oct 18Oct 22Oct 25Oct 28Nov 2
20°FOct 11Oct 19Oct 23Oct 27Oct 30Nov 1Nov 3Nov 6Nov 11
16°FOct 25Oct 30Nov 1Nov 3Nov 5Nov 8Nov 11Nov 14Nov 20

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°F13713012512111711411010597
32°F155149145141137133129124118
28°F175168163159155152147143135
24°F198191185181176172167161154
20°F218211206202197193188181174
16°F232226222218215211207202195

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
9,471
Cooling degree days, base 65°F
392
Growing degree days, base 40°F
3,844
Growing degree days, base 45°F
2,923
Growing degree days, base 50°F
2,111
Growing degree days, base 55°F
1,407
Growing degree days, base 60°F
826

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,82700
February1,54000
March1,25602
April716031
May34718201
June8583450
July29145581
August52109522
September23733271
October660351
November1,12401
December1,60000

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 31.8 km from Fertile. 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 USC00210018 (Ada). Public domain.