Following a second day where temperatures struggled to escape the 30s, and wind chill temperatures held in the 20s for much of the day in most areas, overnight temperatures slid back to or below the freezing point (32 degrees) across much of the region during the late night through the early morning hours of January 3rd. Unlike the prior two mornings, where pockets of light drizzle fell with the freezing temperatures to create conversational glaze ice, January 3rd was precipitation free, after light precipitation fell in the form of a cold light rain during the evening of the 2nd.
Sunshine finally arrived to most areas on the 3rd, allowing temperatures to rise into the lower 50s by afternoon.  With lighter north winds and dry low levels, the stage was set for the coldest morning, area wide, on January 4th.

Frost/Freeze in BROOKS, TEXAS
From 03-JAN-18 05:30:00 to 03-JAN-18 08:30:00 (CST-6)
Reported by: COOP Observer

The cooperative observation station 3 miles west of Falfurrias recorded a low of 31 degrees toward daybreak on January 3rd. Based on proxy observations in western Kenedy County and northern Hidalgo County, low temperatures in some ranch areas likely dropped a bit lower.

Frost/Freeze in KENEDY, TEXAS
From 03-JAN-18 05:30:00 to 03-JAN-18 08:30:00 (CST-6)
Reported by: COOP Observer

The cooperative observation stations 7 miles east of Sarita and 4 miles southeast of Armstrong recorded minimum temperatures of 29 and 28 degrees, respectively, shortly after daybreak on January 3rd.  Kingsville Naval Air Station, about 22 miles north of Sarita, dipped to 26 degrees around 8 AM before the sun finally brought a relative warming trend. Times were estimated based on the Kingsville observations and those from northern Hidalgo County.

Frost/Freeze in WILLACY, TEXAS
From 03-JAN-18 05:30:00 to 03-JAN-18 08:30:00 (CST-6)
Reported by: COOP Observer

The cooperative observation station at Raymondville recorded a minimum temperature of 29 degrees shortly after daybreak on January 3rd.  Proxy observations at Port Mansfield (coastal Willacy, at 31 degrees) and San Manuel (northeast Hidalgo), as well as Armstrong, Kenedy County (28 degrees) made the case for all of the county to have reached 32 degrees or lower for at least two hours.

Frost/Freeze in HIDALGO, TEXAS
From 03-JAN-18 06:00:00 to 03-JAN-18 08:00:00 (CST-6)
Reported by: RAWS

The mesowest/RAWS station at San Manuel dipped to 30 degrees around daybreak on January 3rd; Weslaco AWOS fell to 32 between midnight and 1230 AM, but other county sites (such as Edinburg AWOS) remained above freezing at that time. With the exception of the Rio Grande, county locations reached 32 degrees or slightly lower for a couple hours early on the 3rd, mainly between 6 and 8 AM.

Frost/Freeze in STARR, TEXAS
From 03-JAN-18 05:00:00 to 03-JAN-18 09:00:00 (CST-6)
Reported by: COOP Observer

The cooperative observation station at Rio Grande City fell to 30 degrees around or shortly after sunrise on January 3rd; the Mesowest/RAWS site at Falcon Lake touched 32 degrees. Proxy stations at Zapata County Airport and Hebbronville/Jim Hogg County suggest ranch communities in central and northern Starr County fell to around or just below freezing for several hours before and just after sunrise.
mesowest/RAWS station at San Manuel dipped to 30 degrees around daybreak on January 3rd; Weslaco AWOS fell to 32 between midnight and 1230 AM, but other county sites (such as Edinburg AWOS) remained above freezing at that time. With the exception of the Rio Grande, county locations reached 32 degrees or slightly lower for a couple hours early on the 3rd, mainly between 6 and 8 AM.

Frost/Freeze in JIM HOGG, TEXAS
From 02-JAN-18 19:30:00 to 03-JAN-18 09:00:00 (CST-6)
Reported by: AWOS

The AWOS station at Jim Hogg County Airport, as well as the nearby Mesowest site at the same location (4 miles northwest of Hebbronville) recorded another prolonged freeze that began a couple hours after sunset on the 2nd and continue until a couple hours after sunrise on the 3rd. Low temperatures bottomed out at 27 degrees, with proxy data farther south suggesting upper 20s to around 30 for minimum values. Duration of freezing temperatures likely ranged from 4 to 12 hours, with longest duration across the northern tier where the density of population is largest.

Frost/Freeze in ZAPATA, TEXAS
From 03-JAN-18 03:00:00 to 03-JAN-18 09:00:00 (CST-6)
Reported by: AWOS

The AWOS station at Zapata County Airport dipped to 32 for six hours between 3 and 9 AM on the 3rd. Based on proxy observations in Jim Hogg County, eastern sections of  Zapata may have fallen a degree or two lower.