Brown County climate

Brown County Frost Dates and Growing Season

NOAA 1991-2020 normals for Columbia 8 N, 15.3 km from Brown County, elevation 1305 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Columbia 8 N. 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 7 and the first fall freeze around September 29, a growing season of about 145 days.

Median at 36°F
last May 18, first September 22
Median at 32°F
last May 7, first September 29
Median at 28°F
last April 28, 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°FMay 30May 26May 23May 20May 18May 15May 12May 8May 4
32°FMay 22May 16May 12May 9May 7May 4May 2Apr 30Apr 26
28°FMay 12May 6May 3Apr 30Apr 28Apr 26Apr 22Apr 19Apr 14
24°FMay 3Apr 29Apr 24Apr 21Apr 18Apr 16Apr 13Apr 10Apr 5
20°FApr 25Apr 19Apr 15Apr 12Apr 9Apr 7Apr 4Apr 2Mar 28
16°FApr 15Apr 10Apr 7Apr 4Apr 2Mar 31Mar 26Mar 21Mar 16

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 10Sep 14Sep 17Sep 20Sep 22Sep 24Sep 26Sep 29Oct 3
32°FSep 18Sep 22Sep 24Sep 27Sep 29Oct 1Oct 3Oct 7Oct 12
28°FSep 25Sep 29Oct 2Oct 4Oct 7Oct 10Oct 13Oct 17Oct 22
24°FOct 2Oct 7Oct 11Oct 14Oct 17Oct 20Oct 23Oct 27Nov 1
20°FOct 11Oct 16Oct 21Oct 24Oct 27Oct 30Nov 1Nov 5Nov 10
16°FOct 21Oct 27Oct 31Nov 2Nov 4Nov 6Nov 10Nov 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°F144138134130126123120115109
32°F163156151148145141138134127
28°F180174170165162158154150144
24°F201195189185181177173168161
20°F220213208204200195192186180
16°F238232226222216213208204196

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
8,589
Cooling degree days, base 65°F
558
Growing degree days, base 40°F
4,263
Growing degree days, base 45°F
3,294
Growing degree days, base 50°F
2,436
Growing degree days, base 55°F
1,688
Growing degree days, base 60°F
1,056

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,67500
February1,38700
March1,13203
April656143
May28723245
June61113503
July15216666
August30159594
September19743315
October614265
November1,05002
December1,48500

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 15.3 km from Brown 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 USC00391873 (Columbia 8 N). Public domain.