Brownsville climate

Brownsville Frost Dates and Growing Season

NOAA 1991-2020 normals for Foster Dam, 24.9 km from Brownsville, elevation 550 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Foster 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 April 12 and the first fall freeze around October 28, a growing season of about 197 days.

Median at 36°F
last May 6, first October 6
Median at 32°F
last April 12, first October 28
Median at 28°F
last March 9, first November 18

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°FMay 25May 17May 13May 10May 6May 3Apr 30Apr 26Apr 17
32°FMay 5Apr 30Apr 24Apr 18Apr 12Apr 6Apr 1Mar 26Mar 16
28°FApr 11Mar 28Mar 21Mar 14Mar 9Mar 3Feb 27Feb 20Feb 12
24°FMar 6Feb 28Feb 21Feb 16Feb 9Jan 31Jan 20Jan 6Dec 22
20°FFeb 21Feb 12Jan 30Jan 17Jan 7Jan 1Dec 24Dec 16Dec 4
16°FJan 25Jan 12Jan 1Dec 31Dec 22Dec 16Dec 11Dec 5Dec 1

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°FSep 14Sep 20Sep 27Oct 2Oct 6Oct 10Oct 15Oct 20Oct 27
32°FOct 5Oct 14Oct 20Oct 24Oct 28Nov 1Nov 6Nov 13Nov 21
28°FOct 25Nov 1Nov 6Nov 13Nov 18Nov 23Nov 30Dec 5Dec 16
24°FNov 8Nov 17Nov 27Dec 2Dec 8Dec 16Dec 24Jan 1Jan 18
20°FNov 20Dec 1Dec 7Dec 14Dec 21Dec 30Jan 4Jan 16Feb 7
16°FNov 27Dec 1Dec 7Dec 13Dec 17Dec 27Dec 31Jan 6Jan 19

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°F182171164159153147141136125
32°F233219210204197191183176165
28°F296280269262252244236227214
24°F357340331321313304293281264
20°F365365365363354343334326311
16°F365365365365365365365363343

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
95% of years
20°F or colder
60% of years
16°F or colder
22% 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
4,811
Cooling degree days, base 65°F
233
Growing degree days, base 40°F
4,733
Growing degree days, base 45°F
3,270
Growing degree days, base 50°F
2,111
Growing degree days, base 55°F
1,242
Growing degree days, base 60°F
618

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January74703
February62006
March583025
April452164
May3026185
June16022313
July4486507
August4388510
September13230349
October3731127
November593021
December76304

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 24.9 km from Brownsville. 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 USC00353047 (Foster Dam). Public domain.