Madison County climate

Madison County Frost Dates and Growing Season

NOAA 1991-2020 normals for Rexburg Byu Idaho, 10.8 km from Madison County, elevation 5005 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rexburg Byu Idaho. 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 12 and the first fall freeze around September 24, a growing season of about 132 days.

Median at 36°F
last June 4, first September 11
Median at 32°F
last May 12, first September 24
Median at 28°F
last April 30, first October 7

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 16Jun 11Jun 8Jun 4May 31May 27May 22May 16
32°FJun 2May 27May 20May 15May 12May 9May 6May 3Apr 29
28°FMay 14May 9May 5May 2Apr 30Apr 26Apr 23Apr 18Apr 12
24°FMay 4Apr 27Apr 23Apr 19Apr 15Apr 11Apr 7Apr 3Mar 29
20°FApr 20Apr 13Apr 6Apr 3Mar 30Mar 27Mar 22Mar 17Mar 11
16°FApr 5Mar 30Mar 24Mar 19Mar 16Mar 12Mar 9Mar 6Mar 1

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°FAug 28Sep 2Sep 5Sep 8Sep 11Sep 14Sep 17Sep 21Sep 25
32°FSep 6Sep 12Sep 17Sep 21Sep 24Sep 27Oct 1Oct 4Oct 8
28°FSep 20Sep 27Oct 1Oct 4Oct 7Oct 10Oct 13Oct 17Oct 21
24°FOct 2Oct 8Oct 12Oct 17Oct 20Oct 23Oct 26Oct 30Nov 4
20°FOct 15Oct 20Oct 24Oct 28Oct 31Nov 3Nov 7Nov 12Nov 17
16°FOct 25Oct 31Nov 2Nov 7Nov 11Nov 14Nov 18Nov 22Nov 28

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°F1211131071029893908375
32°F154147142137132127122115107
28°F181175170165161157152146137
24°F209202197192187181176170161
20°F237229223217212207202197189
16°F260252246242236232226219211

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
7,636
Cooling degree days, base 65°F
299
Growing degree days, base 40°F
3,797
Growing degree days, base 45°F
2,792
Growing degree days, base 50°F
1,948
Growing degree days, base 55°F
1,252
Growing degree days, base 60°F
699

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,33800
February1,10600
March90202
April614030
May3604156
June15233337
July28136573
August41108532
September21918269
October600046
November96303
December1,31400

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 10.8 km from Madison County. 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 USC00107644 (Rexburg Byu Idaho). Public domain.