Brown County climate

Brown County Frost Dates and Growing Season

NOAA 1991-2020 normals for Bloomington Indiana Univ, 25.5 km from Brown County, elevation 830 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bloomington Indiana Univ. 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 15 and the first fall freeze around October 26, a growing season of about 192 days.

Median at 36°F
last April 28, first October 16
Median at 32°F
last April 15, first October 26
Median at 28°F
last April 2, first November 4

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 14May 8May 4Apr 30Apr 28Apr 24Apr 20Apr 16Apr 11
32°FMay 3Apr 28Apr 22Apr 18Apr 15Apr 10Apr 7Apr 4Mar 31
28°FApr 22Apr 14Apr 9Apr 5Apr 2Mar 31Mar 29Mar 25Mar 19
24°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 21Mar 18Mar 14Mar 8
20°FMar 31Mar 25Mar 21Mar 17Mar 14Mar 11Mar 8Mar 3Feb 26
16°FMar 20Mar 16Mar 12Mar 8Mar 4Mar 1Feb 25Feb 18Feb 9

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 1Oct 6Oct 10Oct 13Oct 16Oct 19Oct 21Oct 24Oct 28
32°FOct 11Oct 18Oct 21Oct 24Oct 26Oct 29Oct 31Nov 2Nov 9
28°FOct 23Oct 28Oct 31Nov 1Nov 4Nov 8Nov 11Nov 15Nov 21
24°FNov 3Nov 7Nov 11Nov 14Nov 17Nov 20Nov 24Nov 29Dec 3
20°FNov 11Nov 16Nov 20Nov 24Nov 28Dec 1Dec 4Dec 9Dec 16
16°FNov 20Nov 26Dec 1Dec 4Dec 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°F192186179174170166161157149
32°F214206201196192188183176169
28°F238230224219216212207200191
24°F261254248243239234229223216
20°F284275269264260255249243235
16°F307297289283278273267262253

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
5,281
Cooling degree days, base 65°F
1,069
Growing degree days, base 40°F
6,009
Growing degree days, base 45°F
4,747
Growing degree days, base 50°F
3,624
Growing degree days, base 55°F
2,632
Growing degree days, base 60°F
1,780

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12205
February90908
March714355
April36515179
May13783417
June18222654
July2312775
August3282744
September66130516
October32021214
November649150
December97608

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 25.5 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 USC00120784 (Bloomington Indiana Univ). Public domain.