Ravensworth climate

Ravensworth Frost Dates and Growing Season

NOAA 1991-2020 normals for Vienna, 11.5 km from Ravensworth, elevation 418 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Vienna. 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 14 and the first fall freeze around October 29, a growing season of about 198 days.

Median at 36°F
last April 25, first October 19
Median at 32°F
last April 14, first October 29
Median at 28°F
last April 2, first November 8

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 10May 4May 1Apr 29Apr 25Apr 22Apr 19Apr 16Apr 11
32°FApr 28Apr 23Apr 20Apr 16Apr 14Apr 10Apr 7Apr 3Mar 30
28°FApr 16Apr 11Apr 7Apr 5Apr 2Mar 31Mar 27Mar 23Mar 18
24°FApr 5Mar 31Mar 29Mar 25Mar 22Mar 19Mar 16Mar 11Mar 4
20°FMar 24Mar 19Mar 16Mar 12Mar 9Mar 6Mar 2Feb 27Feb 20
16°FMar 16Mar 9Mar 5Mar 1Feb 27Feb 22Feb 17Feb 10Feb 3

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

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°F196189185182178174169165158
32°F218211206202198195191186180
28°F243235230225221217214209203
24°F270262256251246241237232225
20°F297290284280273268263257249
16°F326315308303299294289282273

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
4,931
Cooling degree days, base 65°F
964
Growing degree days, base 40°F
5,911
Growing degree days, base 45°F
4,613
Growing degree days, base 50°F
3,472
Growing degree days, base 55°F
2,480
Growing degree days, base 60°F
1,645

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January99708
February84607
March700143
April37313160
May15658372
June24181608
July1317781
August3271733
September62107496
October31514203
November595148
December861014

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 11.5 km from Ravensworth. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00448737 (Vienna). Public domain.