Winter storage advise?

I live in Florida, but we've had some cold snaps below freezing and it's been in the teens a few times over the last few decades. My car stays in the trailer. But instead of draining the coolant, which is water and a coolant/lubricant additive (no antifreeze), I hang a drop-light with a 60w (more if the fixture is designed for it) incandescent bulb under the hood. Under the water pump, between the engine & radiator, is a good spot. (The new-fangled bulbs don't put out enough heat.) Two couldn't hurt. But it should be just enough to prevent freezing.