Compression of air near the surface, aided by northwesterly flow in the mid and high levels of the atmosphere, returned very hot temperatures to portions of the Rio Grande Valley to close July.  The movement of a surface front into South Central Texas helped draw higher surface moisture into the region.  The result was a two day period of heat index at or above 111F for several hours each afternoon, with overnight temperatures remaining largely in the 80s in most areas.

Heat in STARR, TEXAS
From 30-JUL-09 11:30:00 to 31-JUL-09 16:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat index values, which commonly held between 103 and 108 for most July days in the Rio Grande Valley between Cameron and Zapata County, nudged upward above critical values beginning on the 30th and ending before sunset on the 31st across Starr County mostly near the Rio Grande River, along and south of Federal Highway 83.  At the Falcon Lake Real-Time Observation Monitor and Analysis Network site along the Starr/Zapata County line, heat index peaked at 117 between 3 and 4 pm CDT on July 30th.  Conditions lasted 2 to 4 hours each afternoon; overnight lows did not fall below 80 in the affected area.
As of this writing, there were no known fatalities or injuries from the high heat in Starr County during this period.

Heat in HIDALGO, TEXAS
From 30-JUL-09 11:30:00 to 31-JUL-09 17:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat index values, which commonly held between 103 and 108 for most July days in the Rio Grande Valley between Cameron and Zapata County, nudged upward above critical values beginning on the 30th and ending before sunset on the 31st.  At McAllen/Miller airport, peak heat index reached 114 on the 30th.  New record highs were set at the airport on each day (106 degrees).  At the Lower Rio Grande Valley National Wildlife Refuge along the extreme southeast Hidalgo and southwest Cameron County line, heat index peaked at 117 between 3 and 4 pm CDT. Critical heat index values lasted 2 to 4 hours each afternoon; overnight temperatures remained near or above 80 degrees.
As of this writing, there were no known fatalities or injuries from the high heat in Hidalgo County during this period.

Heat in ZAPATA, TEXAS
From 30-JUL-09 11:30:00 to 31-JUL-09 16:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat index values, which commonly held between 103 and 108 for most July days in the Rio Grande Valley between Cameron and Zapata County, nudged upward above critical values beginning on the 30th and ending before sunset on the 31st across Zapata County mainly near the Rio Grande River, generally south of the City of Zapata.  At the Falcon Lake Real-Time Observation Monitor and Analysis Network site along the Starr/Zapata County line, heat index peaked at 117 between 3 and 4 pm CDT on July 30th.  Conditions lasted 2 to 4 hours each afternoon; overnight lows did not fall below 80 in the affected area.
As of this writing, there were no known fatalities or injuries from the high heat in Zapata County during this period.

Heat in CAMERON, TEXAS
From 30-JUL-09 11:30:00 to 31-JUL-09 17:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Heat index values, which commonly held between 103 and 108 for most July days in the Rio Grande Valley between Cameron and Zapata County, nudged upward above critical values beginning on the 30th and ending before sunset on the 31st across Cameron County mainly west of Federal Highway 77 and along and south of Federal Highway 83.  At the Lower Rio Grande Valley National Wildlife Refuge along the extreme southeast Hidalgo and southwest Cameron County line, heat index peaked at 117 between 3 and 4 pm CDT.  Duration of the critical heat index was from 2 to 4 hours each afternoon; overnight temperatures largely remained near or above 80.
As of this writing, there were no known fatalities or injuries from the high heat in Cameron County during this period.