Well easiest solution is a disconnect switch at the battery. As soon as you turn it off get out in whatever weather you find yourself, raise the hood and flip the switch. No more problem.
What is the problem. You have a short in one of your car's wires (don't ask which one because I don't know which one it is.) I suspect it is in the charging circuit and the first thing I would check is the voltage regulator if you have a DN style alternator, or the alternator's internal diode pack if an early SI style alternator.
Other suspects are the ignition wiring or the ignition switch. The brake switch or the Hi-Low dimmer switch on your floor boards, as both have a lot of power going through them, or the horn button or turn signal switch in side the steering column. It could be corrosion in the bulkhead connector that forms the back of the fuse block. Or some earlier idiot may have some non-factory wire plugged into the fuse block that powers some accessory (like a non-stock radio) that is drawing from the BAT terminal.
There are as many possibilities as there are wires in your car (and there are more in your car than you think there are). This is why 95% of all electrical problems are fixed by replacing the entire wiring harness. This is because it is too labor intensive (unless you are working for Jay Leno on one of his rare cars) to attempt to diagnose an electrical problem going over and testing every circuit for ground, continuity and resistance, as well as measuring the amperage it conducts to eliminate it as the cause of your problem.
You can buy an universal kit from Painless or American Wire and save money if you are good with electronic circuits; or a direct fit original OEM replacement reproduced part that costs a lot more from one of the repop houses, and just replace what you have now.