Chilly air originating in western Canada settled across all of Deep South Texas overnight on January 13th into the early morning of January 14th, as high pressure settled in.  Clear skies, calm winds, and dry air allowed temperatures to plummet after sunset, reaching the lower and mid 30s in normally colder pockets by midnight, and falling below freezing between midnight and 3 AM on the 14th.  Typically colder pockets had more than 8 hours of subfreezing temperatures; in general, based on the locus of observations in the region, 3 to 6 hours of sub-freezing temperatures occurred in larger, generally rural areas of Deep South Texas.

Frost/Freeze in WILLACY, TEXAS
From 14-JAN-09 02:00:00 to 14-JAN-09 08:00:00 (CST-6)
Reported by: Park/Forest Service

Minimum temperatures fell into the upper 20s in rural areas of western Hidalgo County. At the Linn/San Manuel remote automated weather station in the wildlife refuge in the extreme western portion of the county near the Hidalgo County line, eye level temperatures bottomed out at 26 degrees, initially reaching 32F just before midnight on the 13th. Farther east, at Raymondville, temperatures remained just above freezing, but one can infer several hours of sub freezing temperatures in rural areas west of Federal Highway 77, and perhaps other locations just east of the highway as well.

Frost/Freeze in KENEDY, TEXAS
From 14-JAN-09 02:00:00 to 14-JAN-09 08:00:00 (CST-6)
Reported by: COOP Observer

Minimum temperatures fell into the mid and upper 20s in wind protected areas of Kenedy County. At the cooperative observing station east of Sarita, temperatures fell to 28F, and were likely below freezing for several hours.  Similar readings, perhaps a degree or two lower, were reported at the Armstrong cooperative observing station in the Linn/San Manuel remote automated weather station in the wildlife refuge in the south central portion of the county.

Frost/Freeze in BROOKS, TEXAS
From 14-JAN-09 00:00:00 to 14-JAN-09 08:00:00 (CST-6)
Reported by: COOP Observer

Minimum temperatures fell into the upper 20s in a number of locations, especially rural low lying pockets that are common throughout the eastern half of the county.  At the Hollywood Hunting Camp cooperative site (Falfurrias, TX), the low temperature reached 26F.  Temperatures at Brooks County airport hovered around 32F between 3 AM and 730 AM; a remote automated weather station near the Willacy/Brooks/Hidalgo County line bottomed out at 26F, with temperatures reaching 32 just before midnight on the 13th.

Frost/Freeze in STARR, TEXAS
From 14-JAN-09 02:00:00 to 14-JAN-09 08:00:00 (CST-6)
Reported by: Park/Forest Service

Minimum temperatures likely fell into the upper 20s in rural areas of northern and central Starr County, particularly in slightly lower areas in the northeast, central, and southwest portions of the county. At the Falcon Lake remote automated weather station, just north of the Starr/Zapata County line, minimum temperatures reached 28 degrees, with nearly 5 hours at or below 32F.

Frost/Freeze in HIDALGO, TEXAS
From 14-JAN-09 02:00:00 to 14-JAN-09 08:00:00 (CST-6)
Reported by: Park/Forest Service

Minimum temperatures likely fell into the upper 20s in rural areas of northern Hidalgo County. At the Linn/San Manuel remote automated weather station in the wildlife refuge in extreme western Willacy County near the Hidalgo County line, eye level temperatures bottomed out at 26 degrees, initially reaching 32F just before midnight on the 13th.  Interpolating among this location and surrounding locations to the west, one can infer several hours of sub freezing temperatures generally north of McCook.

Frost/Freeze in JIM HOGG, TEXAS
From 14-JAN-09 00:00:00 to 14-JAN-09 08:00:00 (CST-6)
Reported by: COOP Observer

Minimum temperatures fell into the mid or upper 20s in a number of locations, especially in rural low lying pockets across the county.  At the wind protected Hebbronville cooperative observing station, temperatures bottomed out at 25F; the nearby airport near the Jim Hogg/Duval/Webb County line fell to 32F just before 4 AM, and remained nearly steady until around 8 AM.

Frost/Freeze in ZAPATA, TEXAS
From 14-JAN-09 00:00:00 to 14-JAN-09 08:00:00 (CST-6)
Reported by: Park/Forest Service

Minimum temperatures fell into the mid or upper 20s in rural areas along and near the Rio Grande early on the 14th.  Low temperatures in the mid 20s were observed at the sheltered Zapata Airport, several miles northeast of the city of Zapata.  However, other locations farther south near the Starr County line also fell near or below 32F.  At the Falcon Lake remote automated weather station, minimum temperatures reached 28 degrees, with nearly 5 hours at or below 32.