Boone County climate

Boone County Frost Dates and Growing Season

NOAA 1991-2020 normals for Columbia U Of M, 5.5 km from Boone County, elevation 770 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Columbia U Of M. 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 5 and the first fall freeze around October 31, a growing season of about 207 days.

Median at 36°F
last April 18, first October 20
Median at 32°F
last April 5, first October 31
Median at 28°F
last March 26, first November 9

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°FMay 4Apr 29Apr 24Apr 21Apr 18Apr 14Apr 10Apr 7Apr 2
32°FApr 21Apr 16Apr 12Apr 8Apr 5Apr 2Mar 30Mar 25Mar 19
28°FApr 11Apr 6Apr 2Mar 30Mar 26Mar 23Mar 19Mar 15Mar 8
24°FMar 31Mar 26Mar 23Mar 18Mar 15Mar 12Mar 8Mar 4Feb 27
20°FMar 22Mar 16Mar 13Mar 9Mar 6Mar 3Feb 28Feb 24Feb 18
16°FMar 15Mar 9Mar 6Mar 2Feb 28Feb 24Feb 19Feb 14Feb 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°FOct 6Oct 12Oct 15Oct 17Oct 20Oct 23Oct 25Oct 28Nov 1
32°FOct 17Oct 22Oct 25Oct 28Oct 31Nov 1Nov 4Nov 8Nov 14
28°FOct 27Nov 1Nov 4Nov 6Nov 9Nov 12Nov 15Nov 20Nov 27
24°FNov 5Nov 8Nov 12Nov 15Nov 19Nov 23Nov 27Dec 1Dec 7
20°FNov 10Nov 17Nov 22Nov 26Nov 29Dec 3Dec 7Dec 11Dec 18
16°FNov 20Nov 26Dec 1Dec 5Dec 8Dec 12Dec 17Dec 21Dec 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°F205198193189184180176172165
32°F227220215211207203199194187
28°F251244238233229224219214206
24°F272265260255251246241235227
20°F292285278273269264259253245
16°F313303296291286280275269260

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
4,669
Cooling degree days, base 65°F
1,487
Growing degree days, base 40°F
6,809
Growing degree days, base 45°F
5,471
Growing degree days, base 50°F
4,271
Growing degree days, base 55°F
3,209
Growing degree days, base 60°F
2,282

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,05705
February820018
March594584
April28830239
May92118493
June6301745
July0429894
August1388852
September43174581
October26239277
November583371
December922012

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 5.5 km from Boone 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 USC00231801 (Columbia U Of M). Public domain.