Any time a Hard Freeze Warning is posted, there is inevitably talk of protecting the 4 'Ps' -- people, pets, plants and pipes. While the first 3 'Ps' (people, pets, plants) should be given significant attention tonight, I don't think your pipes will be at much risk in this event.
Let me address a couple of important points. First, while the phrase 'hard freeze' always garners a lot of attention, it really has little scientific meaning. In fact, each National Weather Service (NWS) office in the United States is allowed to use their own criteria to define a hard freeze. In our case, the NWS in Slidell defines a hard freeze as temperatures reaching the mid 20°s or lower for several hours. I'm forecasting a low of 27° for Baton Rouge, so you could argue that it may even be a bit of a stretch for us to meet the definition here in the Capital City. Areas farther north -- along the state line into Mississippi -- are much more likely to at least meet those criteria.
Second, the phrase 'hard freeze' instantly equates with pipe-busting cold for many people. Unfortunately, that's a notion that has really been perpetuated by my peers in the weather business. And it's really a myth. If you watched TV today or checked any local media websites, chances are you were warned to protect your pipes. However, while it's certainly a good idea to have any exposed plumbing protected during the winter months, I just don't think this will be a pipe-buster.
As I mentioned above, I'm forecasting a low of 27° in Baton Rouge. A quick search of the records shows that we've hit a temp of 27° or below 67 times since the start of 2001 (11+ years). That means, on average, we saw temps as cold as we expect Friday morning about 6 times a year during that stretch. Have your pipes frozen 67 times in the last 11 years? Have they even frozen once? Mine sure haven't. We did reach the upper teens in January of 2010 and it seems like I remember hearing a handful of reports of frozen pipes then, but that's about all I can remember.
To be fair, it's not just the actual temperature that determines the degree of a frozen pipe threat. The duration of temps below freezing (below 32°F) also has a lot to do with whether pipes will freeze or not. While some of our northern viewers could see temps at or below freezing for 10-12 hours or more, that's still unlikely to cause widespread problems.
While each home and situation is unique, research done by the Building Research Council at the University of Illinois indicates that the threat of frozen pipes becomes much greater once temps near 20° or below. That's just not in the offing for tonight/Friday morning, even for our northernmost viewers.
Now, let me say this...an hour or so spent around the house at the beginning of each winter can eliminate most of our frozen pipe concerns for a given event. Below is a link from the Red Cross on measures you can take to prevent your pipes from freezing and how to thaw frozen pipes: