Kirby climate

Kirby Frost Dates and Growing Season

NOAA 1991-2020 normals for San Antonio Incarnate Word, 8.4 km from Kirby, elevation 700 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for San Antonio Incarnate Word. 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 25 and the first fall freeze around November 28, a growing season of about 277 days.

Median at 36°F
last March 10, first November 16
Median at 32°F
last February 25, first November 28
Median at 28°F
last February 5, first December 15

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 2Mar 27Mar 20Mar 15Mar 10Mar 6Mar 2Feb 25Feb 18
32°FMar 19Mar 10Mar 5Mar 1Feb 25Feb 20Feb 14Feb 5Jan 28
28°FMar 5Feb 27Feb 20Feb 12Feb 5Jan 31Jan 23Jan 14Dec 31
24°FFeb 25Feb 13Feb 5Jan 30Jan 22Jan 14Jan 7Dec 31Dec 18
20°FFeb 14Feb 5Feb 1Jan 22Jan 14Jan 7Jan 1Dec 29Dec 17
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°FOct 30Nov 4Nov 8Nov 12Nov 16Nov 20Nov 24Nov 29Dec 3
32°FNov 7Nov 14Nov 18Nov 24Nov 28Dec 1Dec 5Dec 11Dec 21
28°FNov 19Nov 28Dec 4Dec 8Dec 15Dec 22Jan 1Jan 6Jan 20
24°FDec 3Dec 11Dec 20Dec 28Jan 1Jan 5Jan 12Jan 22Feb 4
20°FDec 16Dec 23Jan 1Jan 1Jan 6Jan 14Jan 24Feb 3Feb 10
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°F279270262256251246239233223
32°F313303293286277272266258249
28°F356342332324315306299289275
24°F365365365363355345335325311
20°F365365365365365365365364346
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
95% of years
24°F or colder
65% of years
20°F or colder
24% of years
16°F or colder
3% 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
1,527
Cooling degree days, base 65°F
2,995
Growing degree days, base 40°F
10,618
Growing degree days, base 45°F
8,851
Growing degree days, base 50°F
7,164
Growing degree days, base 55°F
5,613
Growing degree days, base 60°F
4,219

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January4208135
February28220201
March15070396
April44156563
May5336797
June0505955
July05911,056
August06111,076
September1425875
October39208634
November19652326
December39012152

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 8.4 km from Kirby. 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 USC00417947 (San Antonio Incarnate Word). Public domain.