Most Dallas winters are fairly mild, there can be some snow and ice, but nothing compared to what folks get up north. However occasionally, every few years climate conditions create an ice storm. This happens mostly in the north eastern US, but does happen in Garland, Texas. What happens is the ground or anything like an automobile or even power lines is below freezing, and rain falls through a layer of cold air just above the surface and gets super-cooled. When the drops hit the object below freezing point, a layer of ice forms. This layer of ice covers the ground, road, autos, homes, and everything else.
It will cool your auto engine down well below freezing, and if there is not enough coolant inside the engine block, ice can form inside the engine. As the volume of ice is greater than water, as it freezes the coolant will expand, and can cause major damage. Damage can include burst pipes and hoses, and in the worst case a cracked engine block. Some level of protection can be provided by metal cups which fill the casting holes during manufacture. These are known as core plugs. It is possible that these can be pushed out without damaging the engine, but have your engine checked out before starting it up by a mechanic. See http://www.youtube.com/watch?v=U9BjgY8ijZk.