Brownsville had only 2 nights below freezing, according to this record. They fared much better than places farther East, like LA, AL and FL.

Here is a link that might be useful:

According to accuweather.com there were not a lot of freezing nights and the coldest night was 29F. Not bad for brownsville and they definitely got lucky this past winter.

Good luck!

Thanks guys for the info. It's good to know that they didn't have it as bad as other areas. Hopefully all the coconut palms there survived.

How far down would frost settle along the coastal regions along the Gulf of Mexico?
25°N latitude has got to be about the limit.

For Las Palmas Norte,

This is from the BBC Weather Centre:

In winter, cold waves or 'northers', can bring near-freezing conditions for a few days to the east coast as far south as Tampico or Veracruz. Snow has fallen as far south as Tampico, which is within the tropics. The west coast is protected from such cold waves by the mountains and plateaux of central Mexico.

That makes a lot of sense. Im sure that areas directly by the water are warmer, but that side of mexico is not tropical until you reach south of the tropic of cancer line.

Good luck!