2. Test Your Antifreeze
It might surprise you, but just having the antifreeze topped up in your radiator isn't a guarantee that your engine is protected from low temperatures. Sometimes antifreeze (also known as coolant) has been diluted with too much water, which can affect its ability to resist the cold. You can get your antifreeze tested by your local mechanic to see exactly how low the thermometer can go before your engine block runs the risk of cracking due to frozen coolant, or you can purchase a simple, inexpensive tool of your own that can do the same job.
If it turns out that your antifreeze is no longer living up to its name, or if it's been several years since you had your cooling system flushed and loaded up with fresh liquids, then you should consider replacing everything you have inside the system. It's inexpensive insurance against the cold that will also help reduce the chance of corrosion inside your engine.