Olney climate

Olney Frost Dates and Growing Season

NOAA 1991-2020 normals for Olney, 1.3 km from Olney, elevation 1195 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Olney. 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 March 31 and the first fall freeze around November 8, a growing season of about 222 days.

Median at 36°F
last April 11, first October 30
Median at 32°F
last March 31, first November 8
Median at 28°F
last March 17, first November 18

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°FApr 28Apr 23Apr 19Apr 15Apr 11Apr 6Apr 3Mar 31Mar 24
32°FApr 18Apr 11Apr 6Apr 2Mar 31Mar 27Mar 22Mar 17Mar 10
28°FApr 5Mar 31Mar 25Mar 21Mar 17Mar 13Mar 9Mar 4Feb 26
24°FMar 23Mar 15Mar 10Mar 6Mar 2Feb 28Feb 24Feb 18Feb 10
20°FMar 9Mar 4Feb 28Feb 24Feb 18Feb 12Feb 7Jan 31Jan 20
16°FMar 2Feb 23Feb 14Feb 7Feb 1Jan 28Jan 21Jan 11Dec 29

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

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°F223216211206201196192187181
32°F245238232227222218213206199
28°F271262254249244240235228220
24°F299288281276271266259252244
20°F336324314307301293286278267
16°F365358347338331324315307294

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
99% of years
16°F or colder
85% 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
2,796
Cooling degree days, base 65°F
2,443
Growing degree days, base 40°F
8,979
Growing degree days, base 45°F
7,379
Growing degree days, base 50°F
5,918
Growing degree days, base 55°F
4,601
Growing degree days, base 60°F
3,440

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January690141
February511275
March32917214
April12972402
May25230670
June1460909
July06061,071
August05921,057
September9349790
October104104471
November36410168
December634152

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 1.3 km from Olney. 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 USC00416636 (Olney). Public domain.