Rainfall and rankings in Deep South Texas for the period October 2010 to May 9 2011 (click to enlarge)
Preliminary driest rainfall rankings across Deep South Texas, October 1 2010 to May 9, 2011. * = At least 25 years of data were missing in long term record.
How Much Longer Until it Rains?
Perhaps Long Enough to Erase all prior Water Year Records Before a Break

The 2010/11 Dry Season and History
Updated May 9th: As the 2011 Drought hurtles along, many are asking: "Just how dry has it been, anyway? Is this some kind of record"? The answers, for many, are "extremely dry", and "yes". Between October 1st, 2010, and May 9th, 2011, total rainfall has averaged within the top 5 driest since records have been kept, in some cases back to the late 19th century. Most locations with sufficient records are in the top three driest all time. All areas west of highway 281 were at all time record, with swaths of the brush country and Rio Grande Plains having less than an inch of rain in more than seven months, on par with desert climates from west Texas to California. Particularly notable are Brownsville, whose 2.70 aggregate now ranked 1st(records date to 1878); and Rio Grande City, whose 1.37 beats all available records dating to 1897/98. Hebbronville, (2.21) ranks driest all time, but was missing more than 10 percent of the days in the period, and more than 30 years of record (records dating to 1904). The map below shows water year (beginning October 1st 2010) percent of normal precipitation through April 18th. Note pockets of southwestern Hidalgo and southeastern Starr County, with less than 5 percent of average. Data in northeast Kenedy County are contaminated by false returns from a Wind Farm along the Laguna Madre.

With virtually no rain having fallen since the last report on April 18th, comparisons between the record values and prior records are becoming more interesting, as the "distance" between new and former records increases. To wit:

  • Brownsville: Prior record, 4.16 inches (1942/43).
  • McAllen/Miller: Prior record, 2.81 inches (1961/62).
  • Port Mansfield: Prior record, 2.39 inches (1942/43).
  • Hebbronville: Prior record, 2.66 inches (1970/71).
  • Falcon Dam: Prior record, 1.71 inches (1970/71).
  • Rio Grande City: Prior record, 1.55 inches (1970/71).
  • La Joya: Prior record, 2.13 inches (2008/09).
  • Mc Cook: Prior record, 2.42 inches (2008/09).
  • Mercedes: Prior record, 2.92 inches (2008/09).
Water year percentage of normal, October 1st 2010 through May 9th for Deep South Texas/Rio Grande Valley (click to enlarge) 

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