Sycamore climate

Sycamore Frost Dates and Growing Season

NOAA 1991-2020 normals for Ashburn 3 Ene, 3.2 km from Sycamore, elevation 435 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ashburn 3 Ene. 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 11 and the first fall freeze around November 20, a growing season of about 256 days.

Median at 36°F
last March 23, first November 7
Median at 32°F
last March 11, first November 20
Median at 28°F
last February 26, first December 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°FApr 9Apr 3Mar 31Mar 27Mar 23Mar 19Mar 16Mar 11Mar 4
32°FMar 29Mar 23Mar 19Mar 15Mar 11Mar 6Mar 2Feb 26Feb 19
28°FMar 17Mar 10Mar 5Mar 1Feb 26Feb 19Feb 13Feb 5Jan 28
24°FMar 3Feb 26Feb 17Feb 10Feb 4Jan 31Jan 27Jan 18Jan 5
20°FFeb 19Feb 9Feb 3Jan 31Jan 27Jan 21Jan 14Jan 8Dec 31
16°FFeb 10Feb 3Jan 31Jan 27Jan 23Jan 17Jan 12Jan 7Jan 2

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 23Oct 29Nov 1Nov 4Nov 7Nov 10Nov 14Nov 18Nov 25
32°FNov 1Nov 7Nov 12Nov 16Nov 20Nov 24Nov 29Dec 4Dec 12
28°FNov 12Nov 21Nov 28Dec 2Dec 6Dec 11Dec 20Dec 28Jan 4
24°FNov 27Dec 5Dec 14Dec 23Dec 29Jan 1Jan 5Jan 13Jan 25
20°FDec 11Dec 24Dec 31Jan 3Jan 6Jan 11Jan 16Jan 25Feb 1
16°FJan 1Jan 3Jan 7Jan 10Jan 15Jan 19Jan 24Jan 29Feb 2

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°F257246239233229224219213207
32°F284275268262256250244237228
28°F321309301293287281275268256
24°F357342333326318311305297284
20°F365365365357348339332324311
16°F365365365365365365365352334

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
93% of years
20°F or colder
69% of years
16°F or colder
32% 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
2,002
Cooling degree days, base 65°F
2,245
Growing degree days, base 40°F
9,419
Growing degree days, base 45°F
7,691
Growing degree days, base 50°F
6,071
Growing degree days, base 55°F
4,618
Growing degree days, base 60°F
3,341

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January538177
February3743115
March22623280
April8181451
May10266721
June0425874
July0490955
August0477942
September2333781
October71119515
November26122236
December4405121

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 3.2 km from Sycamore. 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 USC00090406 (Ashburn 3 Ene). Public domain.