Roby climate

Roby Frost Dates and Growing Season

NOAA 1991-2020 normals for Rotan, 14.5 km from Roby, elevation 1995 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rotan. 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 March 17 and the first fall freeze around November 15, a growing season of about 243 days.

Median at 36°F
last March 30, first November 6
Median at 32°F
last March 17, first November 15
Median at 28°F
last March 4, first November 28

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°FApr 15Apr 8Apr 5Apr 1Mar 30Mar 26Mar 22Mar 16Mar 9
32°FApr 3Mar 30Mar 26Mar 21Mar 17Mar 13Mar 9Mar 4Feb 28
28°FMar 23Mar 16Mar 11Mar 7Mar 4Feb 28Feb 24Feb 18Feb 8
24°FMar 11Mar 5Mar 1Feb 24Feb 17Feb 11Feb 5Jan 31Jan 20
20°FMar 1Feb 19Feb 9Feb 4Jan 31Jan 24Jan 17Jan 9Dec 26
16°FFeb 13Feb 5Jan 31Jan 25Jan 20Jan 14Jan 4Dec 28Dec 18

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 24Oct 29Nov 1Nov 4Nov 6Nov 9Nov 12Nov 15Nov 21
32°FOct 31Nov 5Nov 9Nov 12Nov 15Nov 18Nov 22Nov 27Dec 3
28°FNov 9Nov 15Nov 20Nov 25Nov 28Dec 1Dec 5Dec 9Dec 16
24°FNov 21Nov 28Dec 3Dec 7Dec 12Dec 17Dec 22Dec 29Jan 7
20°FDec 4Dec 11Dec 17Dec 23Dec 29Jan 3Jan 9Jan 16Jan 31
16°FDec 12Dec 19Dec 24Dec 30Jan 3Jan 8Jan 16Jan 24Feb 2

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°F245236231226221217212207200
32°F266259253248243238234228219
28°F294285279273268262257250241
24°F333323312306299293286277267
20°F365357348341333327318306296
16°F365365365365364355346338325

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
87% of years
16°F or colder
54% 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
2,461
Cooling degree days, base 65°F
2,696
Growing degree days, base 40°F
9,532
Growing degree days, base 45°F
7,889
Growing degree days, base 50°F
6,368
Growing degree days, base 55°F
4,987
Growing degree days, base 60°F
3,760

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January622158
February4515105
March28629259
April94118481
May17310758
June0510960
July06251,090
August05951,060
September7354797
October88132517
November32217211
December575174

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 14.5 km from Roby. 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 USC00417782 (Rotan). Public domain.