Sylvan climate

Sylvan Frost Dates and Growing Season

NOAA 1991-2020 normals for Gays Mills, 21.5 km from Sylvan, elevation 689 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Gays Mills. 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 May 3 and the first fall freeze around October 7, a growing season of about 156 days.

Median at 36°F
last May 13, first September 29
Median at 32°F
last May 3, first October 7
Median at 28°F
last April 24, first October 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°FMay 28May 23May 19May 16May 13May 10May 7May 4Apr 30
32°FMay 18May 13May 9May 6May 3Apr 30Apr 28Apr 25Apr 19
28°FMay 9May 4Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14Apr 9
24°FApr 30Apr 23Apr 19Apr 15Apr 11Apr 9Apr 6Apr 3Mar 30
20°FApr 18Apr 11Apr 7Apr 4Apr 2Mar 31Mar 28Mar 23Mar 17
16°FApr 6Apr 1Mar 29Mar 25Mar 22Mar 19Mar 16Mar 12Mar 8

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

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°F155149145143139135131126121
32°F175169164160156152149144137
28°F195187182179175171167163156
24°F218211206201197193187182175
20°F243235229225219215211206196
16°F262255249245240236232226218

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
7,333
Cooling degree days, base 65°F
645
Growing degree days, base 40°F
4,678
Growing degree days, base 45°F
3,624
Growing degree days, base 50°F
2,694
Growing degree days, base 55°F
1,885
Growing degree days, base 60°F
1,195

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,48300
February1,21800
March959114
April561370
May24833273
June42138546
July9227684
August17178626
September14960369
October4985101
November876011
December1,27401

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 21.5 km from Sylvan. 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 USC00473022 (Gays Mills). Public domain.