Cold high pressure settled across Deep South Texas on the evening of January 9th, continuing through the early morning of January 10th.  Clear skies and light winds allowed temperatures to fall rapidly back into the 30s after sunset. After midnight, sheltered or wind protected locations plummeted into the upper teens to lower 20s - another hard freeze - while locations with a continuing 4 to 8 mph northerly wind fell to or just below freezing for several hours. Higher relatively humidity allowed widespread frost to form, thickest in hollows and other low lying areas.

Frost/Freeze in JIM HOGG, TEXAS
From 09-JAN-10 21:45:00 to 10-JAN-10 08:45:00 (CST-6)
Reported by: AWOS

Under clear skies and light winds, temperatures dropped sharply after sunset on the 9th, and reached 32 by mid evening.  Light winds continuing overnight allowed a more gradual fall across northern Jim Hogg County overnight, where Hebbronville airport fell to 27 degrees, and the cooperative site (observation at eye level) fell to 22 degrees.   Freezing temperatures lasted at least 10 hours, with hard freezes, or temperatures below 28 degrees, estimated to last from 4 to 8 hours, most prevalent in low lying, wind protected areas - between 1 and 7 AM.
Damage to grazing lands or tender vegetation was unknown as of this writing.

Frost/Freeze in ZAPATA, TEXAS
From 09-JAN-10 22:00:00 to 10-JAN-10 08:30:00 (CST-6)
Reported by: AWOS

Clear, calm conditions allowed temperatures to plummet after sunset on the 9th across the Rio Grande Plains of Zapata County, reaching the freezing point by mid evening on its way down to near 20 degrees in rural pockets, and 20 to 25 degrees elsewhere, by daybreak on the 10th.  Temperatures touched 19 at Zapata County Airport in Medina and fell to 25 near Escobas; freezing temperatures lasted up to 10 and one half hours, with a hard freeze, or temperatures below 28 degrees, lasting between 4 and 8 hours in most areas.
Crop damage, particularly to grazing land, was not reported as of this writing.

Frost/Freeze in WILLACY, TEXAS
From 10-JAN-10 00:30:00 to 10-JAN-10 08:30:00 (CST-6)
Reported by: COOP Observer

Clear, generally calm conditions allowed temperatures to fall rapidly after sunset on the 9th, with readings reaching the freezing point shortly after midnight on the 10th and continuing for an hour after daybreak on the 10th.  Low temperatures early on the 10th range from the lower and mid 20s well west of Highway 77 toward Hidalgo County, to around 30 just east of Highway 77.  Raymondville fell to 29 degrees; freezing temperatures lasted generally from 4 to 8 hours, with a local hard freeze, or temperatures below 28, estimated to last from 2 to 4 hours across the western portion of the county.
While additional minor damage to dryland crops and tender vegetation was likely, the overall impact of the freeze for Willacy County was that of a bullet dodged since temperatures between each cold night rebounded into the upper 40s and lower 50s during the afternoon of the 9th.

Frost/Freeze in CAMERON, TEXAS
From 09-JAN-10 23:00:00 to 10-JAN-10 08:00:00 (CST-6)
Reported by: ASOS

Clear, generally calm conditions allowed temperatures to fall rapidly after sunset on the 9th. By late evening, rural pockets and sheltered locations had fallen to 32 degrees, but temperatures would level off the rest of the night as a light north wind combined with a modifying air mass kept reading in the upper 20s for most areas.  Exceptions included wind sheltered locations, which dropped to between 20 and 25 once again.  Duration of freezing temperatures ranged up to 10 hours, with some areas receiving a hard freeze, or several hours of temperatures below 28.  Harlingen/Valley International Airport fell to 27 degrees.
While most areas did not receive a hard freeze, sheltered pockets had generally between 3 and 6 hours, particularly in western and northern Cameron County.
Additional damage was likely with this second night of freezing temperatures, particularly to sugar cane.  Reports on sugar damage will be available later this spring.

Frost/Freeze in STARR, TEXAS
From 09-JAN-10 22:00:00 to 10-JAN-10 08:30:00 (CST-6)
Reported by: COOP Observer

Clear, generally calm conditions allowed temperatures to fall rapidly after sunset on the 9th. By mid to late evening, many locations, particularly away from Highway 83, had fallen below 32 degrees, and temperatures would continue to drop well into the 20s overnight.  Wind protected locations fell to between 20 and 25 once again.  Duration of freezing temperatures ranged up to 10 and one half hours in some cold pockets, with a number of areas having a hard freeze, or temperatures below 28 degrees, for between 3 and 7 hours but locally up to 10 hours.
Eye level temperatures in sheltered locations included 24 degrees at the Falcon Lake remote automated observing system location near the Zapata County line and near Rio Grande City. Inferred low temperatures across the east side of Starr County were in the mid or upper 20s.

Additional damage was likely with this second night of freezing temperatures, particularly to any sugar cane, but also to some citrus leaves and fruit, and tender tropical vegetation.  Damage reports will be available later this spring.

Frost/Freeze in BROOKS, TEXAS
From 09-JAN-10 22:45:00 to 10-JAN-10 08:15:00 (CST-6)
Reported by: AWOS

Clear, calm conditions allowed temperatures to plummet after sunset on the 9th across the hunting grounds and King Ranch of Brooks County, reaching the freezing point by late evening on its way down to near 20 in rural pockets, and upper 20s elsewhere, by daybreak on the 10th.  Temperatures touched 20 at the Falfurrias cooperative site at the Hollywood Hunting Camp, but only fell to 28 at the Brooks County airport, exposed to more wind. Freezing temperatures lasted up to 9 and one half hours, with a hard freeze, or temperatures below 28 degrees, lasting between 3 and 6 hours in locations away from the city of Falfurrias.
Damage to newly planted coastal grasses was noted by the Farm Services Agency of Brooks and Jim Hogg County in eastern Brooks County from the freezing conditions between the 8th and 10th.  Dollar values were not available as of this writing.

Frost/Freeze in COASTAL CAMERON, TEXAS
From 10-JAN-10 03:30:00 to 10-JAN-10 08:00:00 (CST-6)
Reported by: COOP Observer

Clear, generally calm conditions allowed temperatures to fall rapidly after sunset on the 9th. Near the coast, a light breeze from the Gulf arrived overnight, increasing humidity and holding temperatures from dropping much lower than the freezing point.  Along the coast, temperatures did not reach 32; however, locations within 5 miles of the coast likely fell below 32 for 2 to 4 hours.  This included Laguna Atascosa National Wildlife Refuge, which dropped to 31 after 2 AM and remained between 31 and 33 degrees until after sunrise.  The Cameron County Airport near Bayview dropped to 30 and also held near 32 or just above for much of the night.
No additional significant damage was likely with this freeze.

Frost/Freeze in KENEDY, TEXAS
From 09-JAN-10 00:00:00 to 10-JAN-10 08:15:00 (CST-6)
Reported by: AWOS

Clear, calm conditions allowed temperatures to plummet after sunset on the 9th across the King Ranch, reaching the freezing point toward midnight, and bottoming out between 25 and 30 in most areas by daybreak on the 10th.  Temperatures touched 26 at Armstrong, and 30 degrees a bit east of Sarita.  While freezing temperatures lasted an estimated 8 hours or so, an overnight light wind from the Gulf kept a widespread hard freeze from developing.  Estimates from the cooperative sites suggest 2 to 4 hours of hard freeze, or temperatures below 28 degrees, during the pre dawn hours of the 10th.
Information on any grazing land damage was not known as of this writing.

Frost/Freeze in HIDALGO, TEXAS
From 09-JAN-10 20:30:00 to 10-JAN-10 08:30:00 (CST-6)
Reported by: COOP Observer

Clear, generally calm conditions allowed temperatures to fall rapidly after sunset on the 9th. By mid to late evening, rural pockets and sheltered locations had fallen below 32 degrees, and temperatures would continue to drop well into the 20s overnight.  Elsewhere, after an sharp evening drop, readings leveled off for the rest of the night as a light north to northeast wind combined with a modifying air mass kept readings in the upper 20s to around 30 for most areas.  Wind protected locations fell to between 20 and 25 once again.  Duration of freezing temperatures ranged up to 11 and one half hours in some cold pockets, with a number of areas having a hard freeze, or temperatures below 28 degrees, for between 3 and 7 hours but locally up to 10 hours.
Eye level temperatures in sheltered locations included 23 degrees at the Lower RGV National Wildlife Refuge near Linn/San Manuel, and 20 degrees at the Lower RGV National Wildlife Refuge at Santa Ana, just east of Pharr.  Urban locations either touched freezing or stayed above, including Edinburg at 28 degrees, Weslaco at 32 degrees, and McAllen Miller Airport at 35 degrees.
Additional damage was likely with this second night of freezing temperatures, particularly to sugar cane but also to some citrus leaves and fruit, and tropical tender vegetation.  Damage reports will be available later this spring.

Frost/Freeze in COASTAL WILLACY, TEXAS
From 10-JAN-10 03:30:00 to 10-JAN-10 08:00:00 (CST-6)
Reported by: COOP Observer

Clear, generally calm conditions allowed temperatures to fall rapidly after sunset on the 9th. Near the coast, a light breeze from the Gulf arrived overnight, increasing humidity and holding temperatures from dropping much lower than the freezing point.  Along the coast and Laguna Madre, temperatures did not reach 32; however, locations within 5 miles of the coast likely fell below 32 for 2 to 4 hours.
No additional significant damage was likely with this freeze as temperatures hovered near 32 degrees rather than falling well below.