Rocky Ripple climate

Rocky Ripple Frost Dates and Growing Season

NOAA 1991-2020 normals for Castleton 2 S, 10.9 km from Rocky Ripple, elevation 824 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Castleton 2 S. 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 18 and the first fall freeze around October 26, a growing season of about 190 days.

Median at 36°F
last April 30, first October 16
Median at 32°F
last April 18, first October 26
Median at 28°F
last April 5, first November 5

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 16May 10May 6May 2Apr 30Apr 26Apr 23Apr 19Apr 14
32°FMay 6May 1Apr 25Apr 21Apr 18Apr 14Apr 11Apr 7Apr 3
28°FApr 24Apr 17Apr 12Apr 8Apr 5Apr 3Mar 31Mar 27Mar 21
24°FApr 9Apr 3Mar 31Mar 29Mar 25Mar 22Mar 18Mar 14Mar 9
20°FMar 30Mar 25Mar 21Mar 17Mar 13Mar 10Mar 6Mar 2Feb 25
16°FMar 21Mar 15Mar 11Mar 7Mar 4Mar 1Feb 26Feb 19Feb 12

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 3Oct 8Oct 11Oct 13Oct 16Oct 18Oct 21Oct 23Oct 27
32°FOct 12Oct 18Oct 21Oct 24Oct 26Oct 29Oct 31Nov 3Nov 7
28°FOct 25Oct 31Nov 1Nov 3Nov 5Nov 8Nov 11Nov 15Nov 21
24°FNov 4Nov 7Nov 11Nov 14Nov 17Nov 21Nov 24Nov 30Dec 5
20°FNov 10Nov 15Nov 20Nov 24Nov 28Dec 1Dec 5Dec 9Dec 15
16°FNov 18Nov 25Nov 30Dec 3Dec 6Dec 10Dec 15Dec 20Dec 26

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°F187181176172167163159154147
32°F211203198195190186180174166
28°F235227222217213210205200192
24°F259252246242237233229224217
20°F281273267262257253247242234
16°F303296289283277273267261251

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
5,428
Cooling degree days, base 65°F
999
Growing degree days, base 40°F
5,859
Growing degree days, base 45°F
4,619
Growing degree days, base 50°F
3,518
Growing degree days, base 55°F
2,546
Growing degree days, base 60°F
1,702

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,15502
February93407
March726458
April3648170
May14077409
June10214654
July2311773
August4255716
September76115490
October33915194
November673140
December1,00604

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 10.9 km from Rocky Ripple. 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 USC00121326 (Castleton 2 S). Public domain.