A History of Severe Freezes in the Lower Rio Grande Valley -- Part III
by Richard Travis
(This is the last in a 3-part series on a history of hard freezes in the Lower Valley. This part covers the two severe freezes in the 1980's, with a comparison of the severity of these two freezes versus previous freezes in the Valley.)
After 1962, it would be 22 seasons until the next severe freeze. The seventies saw a number of cool to cold winters, but none of these produced any really serious threats to the Valley. The eighties would not be as kind. In January 1982, the strongest cold wave since the early 1960's blew through Texas. This front moved quickly, however, and the Valley was pretty much spared, with temperatures no lower than the mid- to upper-twenties. But nearly two years later the Valley would not be so lucky.
December 1983: The first bad freeze of the decade arrived in Brownsville on Christmas Eve 1983. Very cold weather had been entrenched in Texas for over a week when the big blow hit -- North Texas had experienced day after day of subfreezing weather, which each front colder than the previous. The low latitude of far South Texas had protected the area from the first few fronts, but on the 24th a severely cold air mass arrived which spared no area of the state. The temperature that day in Brownsville began sinking from 39° at midnight to 31° at 6:00 a.m. and 25° by noon, with an absolute minimum of 20° the next morning. The following is the temperature data from the 24th to 26th at 6-hour intervals:
Most of the Valley was slightly colder -- McAllen recorded 19° and Weslaco had 17°. Though slightly shorter than the outbreaks of 1951 and 1962, this freeze brought a much longer sustained duration of temperature in the mid-twenties or below. Such a prolonged period of deep-freezing weather had not been seen in Brownsville since the previous century. It particularly resembled the cold outbreaks of 1852, 1873, and 1888.
This freeze may forever be known as the freeze that killed the palm trees in the Valley. Anyone who lived in the Valley before 1983 remembers well the thousands of tall slender Washingtonia robusta lining the local roads for mile after mile. The dead stumps were a sad sight on the Valley skyline for several years afterwards -- some still remain to this day. Citrus also received a good beating, the worst since 1951. The Valley got such a cleaning from 1983 it would almost make the worst freeze of the century seem anticlimactic.
December 1989: Being used to decades of reasonably mild winters, many locals had dismissed 1983 as a real fluke, a once-in-a-century aberration. But six years later, almost to the day after the 1983 freeze, the real "100-year freeze" arrived at the Valley's doorstep. In severity this one took a back seat only to 1899. The 1989 outbreak, in fact, resembled the 1899 freeze in many ways. It was a fast moving, very powerful outbreak of Arctic air which stretched across most of the United States and deep into Mexico and onto the Florida peninsula. Both produced two nights of very low readings in deepest South Texas. The temperature in Brownsville started out in the forties on the 21st, but soon after midnight on the 22nd, the Arctic air began pouring in. By morning, the temperature was entrenched in the twenties. All day, the thermometer hovered around 27°. Then that night, the worst happened: the skies cleared. This sent readings plummeting from 23° at midnight to 16° the next morning, even with the wind blowing through the night. The 23rd was bright and sunny, but managed to get no warmer than 34°. The next night started out even colder than the previous due to the lack of wind. By midnight, it was already 21° degrees, but fortunately the Arctic high was already moving away and the mercury did not drop more than 3° afterwards. Conditions warmed rapidly the next day. The temperatures from Brownsville again follow:
Unlike 1983, the 1989 freeze was slightly colder toward the coast. The minimum temperature in McAllen was only 18°, whereas Weslaco again saw 17°. Nevertheless, this was still the only freeze in the twentieth century to produce two nights of sub-20° readings across all of South Texas.
Since the 1989 freeze, the winters have fortunately seemed to have modified over the 80's. Another hard freeze could certainly occur any time, but it seems that severe freezes are not totally random judging from historical records. There is good evidence that cold winters tend to come in cycles, the most notable example being the late 1800's with the 1980's a more recent instance.
When comparing freezes, the question is inevitably asked as to which freeze(s) were the worst. That, of course, is an often subjective question. The worst freeze for a meteorologist may be entirely different than one for a citrus or palm grower. Even if one were to look at nothing but the data, there is still some room for debate when ranking the freezes. If I were asked to come up with such a list, I would have to take several factors into consideration. Absolute minimum temperatures, number of hours below freezing, number of consecutive hours in a "deep freeze" (mid-twenties or below), and conditions during the coldest temperatures (i.e., wind speed and cloudiness) would all be factors. Using that criteria, there are three or four freezes which really stand out. The Great Arctic Outbreak of 1899 would easily top the list, it simply has no equal. Coming in second would have to be 1989, with the longer (but less cold) freeze of the 1880-1 a pretty close third. After that, the four similar freezes of 1852, 1873, 1888, and 1983 are all contenders for fourth place, with 1888 getting the nod since it apparently had more hours in the low twenties.
For plant people, the list of worst freezes would look completely different. Gone would be the cold waves of the 1800's, there was simply not enough tender vegetation to destroy 100 years ago. The freezes of the 1980's would be near the top, with 1983 getting the higher rank since there was more to kill the first time around. But first place has to go to the relative tepid 1951 freeze. Other than being very long, it did not produce the extended periods in the low- to mid-twenties of stronger freezes. What made this one so bad was its timing. It came after a half-century of mild weather, a period which had seen an explosion of subtropical fruit and ornamental plantings in South Texas. And worse yet, the freeze hit late in the season, during a mild winter, when many plants had already resumed growth. What resulted was the worst botanical slaughter in South Texas history.
There Are Lies...
With a century and a half of weather records, it should be possible to get some statistical idea of the frequency of severe freezes in South Texas. Among all the freezes, there are at least 9 or 10 which could be classified as prolonged hard freezes. For palm trees, this would be a freeze hard enough to kill queen palms, (Syagrus romanzoffianum) or older, weaker Mexican fan palms (Washingtonia robusta). There are surprisingly few freezes which are "borderline" cases in Brownsville -- freezes which are either fairly hard or prolonged but not both. Such examples would include 1850, 1875, 1886, and 1949 (1895 might also belong here -- critical data is missing from that spell). So for 150 years of weather records and 9 or 10 really bad freezes, that would be an average of one ever 15 or 16 years.
A more useful statistic might be the intervals between hard freezes. The first two severe freezes in recorded Valley history came in 1852 and 1873 -- that's an interval of 21 years. Doing some quick and dirty statistical analysis on the numbers, it is found that the interval between the "big ones" has ranged from 4 or 6 years to 52 years. So, while the average time between hard freezes may be 16 to 19 years, the median time between such spells is only 10 or 11 years. The median indicates that, half of the time, the interval between hard freezes has been less than 11 years apart, while the other half of the time the interval has been more than 11 years apart. If you were to exclude that exceptionally cold period between 1880 and 1900 when analyzing the data, the mean and median intervals do not change too dramatically. For example, the average (mean) time between hard freezes increases to 20 years instead of 16 to 19 years while the median time between freezes increases from 11 year to 16 years. A very coarse estimate would be to approximate a median interval of 15 years between the most destructive cold waves, though this time can be highly variable (from a half-decade to a half-century). Predicting when the next big one will arrive is really anybody's guess.
Summary of severe freezes, 1847-1996 (those marked with a "*" indicate a prolonged severe freeze [somewhat subjectively] )
This article originally appeared in the Palm Society of South Texas Bulletin and is available on the internet with the author's permission.
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