Cold weather is tough on batteries
Cold weather is tough on batteries—not so much because it does damage to them, but because it requires a lot more FROM them. Vehicles that have been sitting out in the cold on a long winter night are harder to start than they would be if it were a morning in the middle of July. This is in large part because the oil in them is thick. One way of explaining this effect is to think of your engine and the oil inside like a can of a cream-style soup (cream of mushroom or clam chowder for example). When you open the can cold, the soup is thick and congealed; it takes a lot of effort to get it out of there, to get it moving so to speak. You have to shake the can or get a spoon and scrape the thick stuff out. But, once it’s in the pan and warms up, it softens and becomes liquid that is easy to pour.
Well, that’s essentially what’s happening inside your vehicle’s engine on cold winter mornings: the oil inside has gotten thick (conventional oil thickens—synthetic oils are designed to avoid this effect). The colder it is, the more thickening takes place. When you get in and turn the key, your vehicle’s starter has to crank an engine full of cold, thick oil that doesn't move as well as warm oil does. Since the battery is where the starter gets its energy, the battery has to provide a lot more electricity to get the engine going given all that cold, goopy oil inside.
Another cold-related issue for batteries is that the processes by which they produce electrons are chemical, and those chemicals aren't as active when cold. So they actually produce less electricity at this time of year. A battery that works at 100% capacity when it is 80°F will be down to 65% when the temperature is 32°F. It’s down to 40% if the temperature hits 0°F. Given what we just covered up above, this is a problem: the battery is producing less electricity in the cold, right when more electricity is what we need. Before the cold weather finds you stuck some morning soon, get your vehicle’s battery, battery cables and charging system checked. A bit of prevention can save you some headaches down the road.