Blairs climate

Blairs Frost Dates and Growing Season

NOAA 1991-2020 normals for Danville Rgnl AP, 12.4 km from Blairs, elevation 571 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Danville Rgnl AP. 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 10 and the first fall freeze around October 28, a growing season of about 200 days.

Median at 36°F
last April 23, first October 20
Median at 32°F
last April 10, first October 28
Median at 28°F
last March 30, first November 6

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 12May 5Apr 30Apr 27Apr 23Apr 20Apr 16Apr 12Apr 7
32°FMay 1Apr 22Apr 18Apr 14Apr 10Apr 7Apr 4Mar 31Mar 26
28°FApr 13Apr 8Apr 4Apr 1Mar 30Mar 26Mar 22Mar 17Mar 11
24°FApr 3Mar 29Mar 24Mar 20Mar 16Mar 12Mar 7Mar 1Feb 24
20°FMar 21Mar 15Mar 10Mar 5Mar 1Feb 25Feb 20Feb 14Feb 4
16°FMar 10Mar 1Feb 23Feb 17Feb 11Feb 5Jan 31Jan 24Jan 13

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

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°F199193188183178173169164156
32°F223214209204200195190184176
28°F247239233228223219214209201
24°F279268260254249244239233224
20°F315304295287280274266258248
16°F353337329322314308300292278

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
96% 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
3,808
Cooling degree days, base 65°F
1,382
Growing degree days, base 40°F
7,058
Growing degree days, base 45°F
5,602
Growing degree days, base 50°F
4,314
Growing degree days, base 55°F
3,183
Growing degree days, base 60°F
2,203

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January821017
February660129
March5035106
April23829267
May77108497
June4273718
July0400865
August1357821
September29178599
October22430289
November509279
December743028

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 12.4 km from Blairs. 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 USW00013728 (Danville Rgnl AP). Public domain.