Comal County climate

Comal County Frost Dates and Growing Season

NOAA 1991-2020 normals for Canyon Dam, 9.9 km from Comal County, elevation 1000 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Canyon Dam. 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 1 and the first fall freeze around December 1, a growing season of about 276 days.

Median at 36°F
last March 12, first November 16
Median at 32°F
last March 1, first December 1
Median at 28°F
last February 10, first December 19

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 4Mar 28Mar 21Mar 17Mar 12Mar 8Mar 4Feb 28Feb 21
32°FMar 22Mar 13Mar 8Mar 4Mar 1Feb 25Feb 20Feb 13Jan 31
28°FMar 9Mar 2Feb 24Feb 16Feb 10Feb 1Jan 27Jan 18Jan 4
24°FFeb 28Feb 18Feb 9Feb 1Jan 25Jan 18Jan 9Jan 2Dec 25
20°FFeb 16Feb 9Jan 31Jan 22Jan 18Jan 10Jan 6Jan 2Dec 29
16°F–––––––––

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°FNov 1Nov 4Nov 9Nov 13Nov 16Nov 20Nov 25Nov 30Dec 5
32°FNov 9Nov 17Nov 22Nov 28Dec 1Dec 5Dec 10Dec 15Dec 26
28°FNov 23Dec 1Dec 7Dec 13Dec 19Dec 26Jan 1Jan 9Jan 21
24°FDec 11Dec 21Dec 27Jan 1Jan 5Jan 11Jan 19Feb 1Feb 16
20°FDec 23Dec 31Jan 2Jan 6Jan 12Jan 18Jan 21Feb 2Feb 12
16°F–––––––––

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°F275266260254249243238232220
32°F313299290283276270264254244
28°F351339330319311304296287274
24°F365365365362354346335325311
20°F365365365365365365365365350
16°F365365365365365365365365365

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
96% of years
24°F or colder
65% of years
20°F or colder
24% of years
16°F or colder
4% 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
1,672
Cooling degree days, base 65°F
2,834
Growing degree days, base 40°F
10,329
Growing degree days, base 45°F
8,584
Growing degree days, base 50°F
6,930
Growing degree days, base 55°F
5,404
Growing degree days, base 60°F
4,034

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January4585118
February31712171
March18247350
April52132531
May6316775
June0482931
July05721,037
August05981,063
September2416864
October43200624
November20546318
December4089149

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 9.9 km from Comal County. 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 USC00411429 (Canyon Dam). Public domain.