Leon Valley climate

Leon Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for San Antonio/seaworld, 9.5 km from Leon Valley, elevation 940 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for San Antonio/seaworld. 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 February 18 and the first fall freeze around December 9, a growing season of about 296 days.

Median at 36°F
last March 4, first November 25
Median at 32°F
last February 18, first December 9
Median at 28°F
last January 31, first December 29

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°FMar 31Mar 21Mar 14Mar 9Mar 4Feb 28Feb 24Feb 19Feb 11
32°FMar 16Mar 6Feb 28Feb 23Feb 18Feb 12Feb 5Jan 29Jan 18
28°FMar 3Feb 22Feb 14Feb 6Jan 31Jan 24Jan 14Jan 2Dec 17
24°FFeb 22Feb 10Feb 5Jan 28Jan 19Jan 7Dec 31Dec 20Dec 8
20°F–––––––––
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 5Nov 12Nov 16Nov 21Nov 25Nov 29Dec 3Dec 8Dec 15
32°FNov 17Nov 24Nov 29Dec 4Dec 9Dec 15Dec 24Jan 2Jan 13
28°FNov 28Dec 5Dec 12Dec 19Dec 29Jan 4Jan 10Jan 22Feb 9
24°FDec 4Dec 11Dec 19Dec 26Jan 3Jan 11Jan 23Feb 2Feb 12
20°F–––––––––
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°F297285276269264259252243233
32°F334322313304296289281271260
28°F365365353343334327317304291
24°F365365365365365365355341326
20°F365365365365365365365365365
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
99% of years
28°F or colder
79% of years
24°F or colder
38% of years
20°F or colder
8% of years
16°F or colder
0% 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
1,182
Cooling degree days, base 65°F
3,460
Growing degree days, base 40°F
11,415
Growing degree days, base 45°F
9,625
Growing degree days, base 50°F
7,892
Growing degree days, base 55°F
6,265
Growing degree days, base 60°F
4,780

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January3537174
February22429249
March10689454
April20212643
May1407871
June05611,011
July06431,108
August06651,130
September1495943
October18269717
November13869392
December32315200

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 9.5 km from Leon Valley. 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 USC00418169 (San Antonio/seaworld). Public domain.