Rock Mills climate

Rock Mills Frost Dates and Growing Season

NOAA 1991-2020 normals for Rock Mills, 0.4 km from Rock Mills, elevation 750 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rock 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 April 2 and the first fall freeze around November 3, a growing season of about 216 days.

Median at 36°F
last April 16, first October 24
Median at 32°F
last April 2, first November 3
Median at 28°F
last March 17, first November 14

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 1Apr 27Apr 22Apr 19Apr 16Apr 12Apr 10Apr 5Mar 30
32°FApr 18Apr 13Apr 9Apr 5Apr 2Mar 30Mar 26Mar 20Mar 13
28°FApr 6Mar 31Mar 27Mar 22Mar 17Mar 13Mar 8Mar 3Feb 24
24°FMar 22Mar 15Mar 10Mar 5Feb 28Feb 25Feb 20Feb 12Feb 2
20°FMar 10Mar 1Feb 23Feb 16Feb 9Feb 3Jan 31Jan 24Jan 13
16°FFeb 25Feb 11Feb 4Jan 31Jan 28Jan 23Jan 17Jan 11Dec 31

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 11Oct 15Oct 18Oct 21Oct 24Oct 27Oct 30Nov 2Nov 6
32°FOct 21Oct 25Oct 29Nov 1Nov 3Nov 5Nov 8Nov 12Nov 19
28°FNov 1Nov 4Nov 8Nov 11Nov 14Nov 18Nov 22Nov 27Dec 1
24°FNov 11Nov 18Nov 23Nov 28Dec 1Dec 3Dec 7Dec 14Dec 25
20°FNov 24Dec 1Dec 6Dec 12Dec 20Dec 26Jan 1Jan 7Jan 18
16°FDec 6Dec 16Dec 25Dec 31Jan 3Jan 7Jan 13Jan 21Feb 1

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°F213205200196191187182177171
32°F240231225220216211206199191
28°F272263257251245239232226216
24°F309298289282275270264256247
20°F342333325317310304295287273
16°F365364351344337333326315304

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
98% of years
16°F or colder
79% 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
2,790
Cooling degree days, base 65°F
1,670
Growing degree days, base 40°F
8,141
Growing degree days, base 45°F
6,517
Growing degree days, base 50°F
5,053
Growing degree days, base 55°F
3,746
Growing degree days, base 60°F
2,619

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January676043
February481168
March3278192
April13937355
May29170606
June0333783
July0406871
August0408873
September11247685
October14256386
November3894133
December594159

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 0.4 km from Rock Mills. 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 USC00017025 (Rock Mills). Public domain.