Scissors Frost Dates and Growing Season

NOAA 1991-2020 normals for Weslaco, 9.3 km from Scissors, elevation 75 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Weslaco. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

A freeze (32°F or colder) happens in only 44 percent of years at Weslaco, so there is no typical freeze season.

Median at 36°F: last January 28, first December 19
Median at 32°F: last January 8, first December 31

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Mar 1	Feb 19	Feb 11	Feb 2	Jan 28	Jan 18	Jan 8	Dec 31	Dec 18
32°F	Feb 18	Feb 5	Jan 27	Jan 17	Jan 8	Jan 2	Dec 28	Dec 20	Dec 8
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Nov 25	Dec 1	Dec 5	Dec 12	Dec 19	Dec 25	Jan 1	Jan 7	Jan 27
32°F	Dec 3	Dec 12	Dec 20	Dec 26	Dec 31	Jan 4	Jan 9	Jan 25	Feb 7
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	365	355	346	338	331	324	316	306	292
32°F	365	365	365	365	365	364	355	344	332
28°F	365	365	365	365	365	365	365	365	364
24°F	365	365	365	365	365	365	365	365	365
20°F	365	365	365	365	365	365	365	365	365
16°F	365	365	365	365	365	365	365	365	365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder: 85% of years
32°F or colder: 44% of years
28°F or colder: 10% of years
24°F or colder: 1% of years
20°F or colder: 0% 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: 580
Cooling degree days, base 65°F: 4,251
Growing degree days, base 40°F: 12,799
Growing degree days, base 45°F: 10,984
Growing degree days, base 50°F: 9,194
Growing degree days, base 55°F: 7,450
Growing degree days, base 60°F: 5,790

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	187	53	350
February	107	91	413
March	39	206	634
April	7	328	771
May	0	493	958
June	0	601	1,051
July	0	654	1,119
August	0	677	1,142
September	0	522	972
October	7	366	825
November	61	185	578
December	173	74	381

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 9.3 km from Scissors. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00419588 (Weslaco). Public domain.