Blue Grass climate

Blue Grass Frost Dates and Growing Season

NOAA 1991-2020 normals for Rock Island L&d 15, 16.8 km from Blue Grass, elevation 568 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rock Island L&d 15. 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 19 and the first fall freeze around October 22, a growing season of about 184 days.

Median at 36°F
last April 30, first October 12
Median at 32°F
last April 19, first October 22
Median at 28°F
last April 8, first October 31

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 9May 5May 2Apr 30Apr 27Apr 24Apr 21Apr 16
32°FMay 4Apr 29Apr 24Apr 21Apr 19Apr 16Apr 13Apr 10Apr 6
28°FApr 23Apr 18Apr 14Apr 11Apr 8Apr 6Apr 3Mar 31Mar 25
24°FApr 14Apr 9Apr 5Apr 3Mar 31Mar 29Mar 25Mar 20Mar 15
20°FApr 5Apr 1Mar 28Mar 25Mar 22Mar 18Mar 14Mar 11Mar 5
16°FMar 27Mar 22Mar 18Mar 15Mar 12Mar 9Mar 6Mar 3Feb 26

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 29Oct 3Oct 6Oct 10Oct 12Oct 15Oct 18Oct 20Oct 24
32°FOct 7Oct 13Oct 17Oct 19Oct 22Oct 24Oct 27Oct 30Nov 2
28°FOct 18Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 9Nov 14
24°FOct 28Nov 1Nov 3Nov 6Nov 9Nov 12Nov 15Nov 18Nov 24
20°FNov 4Nov 8Nov 12Nov 15Nov 19Nov 22Nov 25Nov 29Dec 4
16°FNov 11Nov 16Nov 21Nov 25Nov 27Nov 30Dec 2Dec 7Dec 13

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°F183177172168164160156151144
32°F203197191188184181177172164
28°F223216212208204200196191184
24°F243236231227222219214209202
20°F264255250246242238233227220
16°F281274268264260255250245239

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
6,241
Cooling degree days, base 65°F
935
Growing degree days, base 40°F
5,473
Growing degree days, base 45°F
4,326
Growing degree days, base 50°F
3,293
Growing degree days, base 55°F
2,382
Growing degree days, base 60°F
1,593

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,32700
February1,06102
March832128
April4477120
May16962367
June20203633
July2293756
August6246705
September83108478
October37715176
November767027
December1,15202

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 16.8 km from Blue Grass. 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 USC00117391 (Rock Island L&d 15). Public domain.