Beat the Heat at the Beach; no changes expected through July 27 2009
Hottest July Ever?
Not Yet, but All Time Records Are Dropping like Flies

Update to July 14th Information
Like a broken record, the searing heat continues in Deep South Texas. While the region is known for its hot and humid summers, the persistence of the heat, relatively gusty southeast winds, and lack of any widespread rain events for most areas since early June has been impressive. For July, average temperatures through the 22nd were 3.1°F above average at Brownsville, 3.5°F above average at Harlingen, and remained a whopping 6.7°F above average at McAllen. For McAllen's Miller Airport, all but two days surpassed 100°F, with an average high of 104°F! As of this writing, no end was in sight to the heat and largely rain free weather. The continuing dry, breezy, and hot conditions will maintain moderate to exceptional drought across the region and keep a critical threat for rapid wild fire growth.

As of this writing (July 22), no perceptible change is expected to the overall atmospheric pattern (image below), which will continue to feature a strong ridge of heat building high pressure covering the Western U.S. and extending through West and South Texas, and an unusually persistent trough of low pressure extending from the upper Midwest into the Northeast U.S. Between the two systems, weak disturbances will induce periods of strong to locally severe thunderstorms; some which will reach into North and East Texas. Unfortunately for the Rio Grande Valley, this activity will remain well north and east. Even the tropical Gulf of Mexico will be closed off by the persisting north and west flow well above the earth’s surface.

Records to Fall?
A quick glance at average temperatures for 2009 through July 22nd 2009, compared with historical averages since records have been kept, tells the tale. If you thought this was one of the hottest July’s ever, you’re not far off. For all stations referenced in the following table, 2009 ranks at or near the top of the heap. Or is that heat? In less than two weeks, we’ll know for sure.

Average Temperatures, July 2009 (through the 20th, preliminary data)
Station
2009 Average
Rank
All-Time Record
Year
McAllen (since 1941)
92.5
1
90.0
1998
Harlingen (since 1911)
87.8
1
87.6
1998
Weslaco (since 1914*)
88.2**
1
87.8
1980
Port Isabel (since 1928*)
86.9**
1
86.4
1998
Falfurrias (since 1907)
90**
1
89.95
1998
Rio Grande City (since 1900*)
91.1
2
91.8
1998
Hebbronville (since 1917*)
89.3
2
89.6
1998
Falcon Dam (since 1962)
90.4
T-3
91.65
1998
Brownsville (since 1871)
87.0
4
87.5
1980
Raymondville (since 1913*)
88.5**
6
89.8
1947
*Data incomplete, especially early in 20th century.
**July 2009 missing 4 or more dates (incomplete)
Atmospheric pattern which has dominated much of June and July across the U.S. in 2009
General flow pattern between 20 and 30 thousand feet in the atmosphere. White curve with arrow denotes mean jet stream.
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