Rock Hill climate

Rock Hill Frost Dates and Growing Season

NOAA 1991-2020 normals for Rock Hill 3 Sw, 4 km from Rock Hill, elevation 1270 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rock Hill 3 Sw. 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 7 and the first fall freeze around October 7, a growing season of about 152 days.

Median at 36°F
last May 19, first September 28
Median at 32°F
last May 7, first October 7
Median at 28°F
last April 27, first October 20

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°FJun 1May 28May 25May 22May 19May 16May 12May 8May 3
32°FMay 22May 16May 12May 9May 7May 4May 1Apr 28Apr 25
28°FMay 10May 5May 2Apr 30Apr 27Apr 24Apr 22Apr 19Apr 15
24°FApr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 10Apr 7Apr 4
20°FApr 18Apr 14Apr 9Apr 7Apr 4Apr 3Mar 31Mar 28Mar 21
16°FApr 6Apr 2Mar 31Mar 28Mar 24Mar 21Mar 17Mar 14Mar 9

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 15Sep 19Sep 22Sep 25Sep 28Sep 30Oct 2Oct 5Oct 9
32°FSep 25Sep 30Oct 1Oct 4Oct 7Oct 10Oct 12Oct 16Oct 22
28°FOct 4Oct 9Oct 13Oct 17Oct 20Oct 24Oct 27Nov 1Nov 4
24°FOct 18Oct 23Oct 28Nov 1Nov 3Nov 5Nov 8Nov 12Nov 18
20°FNov 1Nov 5Nov 9Nov 13Nov 16Nov 20Nov 22Nov 27Dec 1
16°FNov 12Nov 18Nov 22Nov 25Nov 28Dec 1Dec 4Dec 8Dec 14

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°F150144139134131127123118112
32°F172165160156152149145141135
28°F196189184180176172167163156
24°F220214208204201196192187179
20°F246238233228224221216211205
16°F269262256251247243239233226

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
7,236
Cooling degree days, base 65°F
339
Growing degree days, base 40°F
4,074
Growing degree days, base 45°F
3,050
Growing degree days, base 50°F
2,154
Growing degree days, base 55°F
1,401
Growing degree days, base 60°F
787

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,30500
February1,15600
March1,02302
April621243
May31412201
June8858421
July22135578
August34104535
September19028294
October517173
November82208
December1,14400

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 4 km from Rock Hill. 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 USC00307210 (Rock Hill 3 Sw). Public domain.