The leading edge of the arctic air is forecast to arrive in our northern counties about 5:am Thursday morning. The front should reach downtown Houston between 6 and 7 am. Here's a look at what to expect as Thursday morning progresses.
At this time we do not expect and significant accumulation of sleet or snow but I expect to see at least some light frozen precip as the temperature drops to freezing late morning/early afternoon.
Once temps drop below freezing expect the area north of the Woodlands to stay below freezing until Saturday afternoon. South of that expect only a brief period of temps above freezing Friday afternoon before quickly falling back below the freezing mark. This is why it is so important to wrap exposed water pipes as they can burst under these conditions. Heavily water and cover the plants you want to try to save, although even then I expect to lose some plants in my yard.