Based on the information here in TFP, I tend to be fairly sanguine about cold weather.
www.troublefreepool.com
Mostly I just extend run times and for overnight temps down to the lower 20's I use a moving blanket and a (getting harder to find) incandescent light bulb.
Several years ago I learned the limits of this approach during a long, deep freeze. My flowmeter and the pressure gauge on my filter, which stick out from the plumbing and have little or no water flowing through them, both froze and had to be replaced.
With an extended hard freeze in the forecast I wanted to use a small ceramic forced-air heater to protect these parts of my system, but I was concerned about flammability of the moving blanket. While perusing Amazon I ran across fireproof, insulating, fiberglass welder's blankets, which are available in a variety of sizes.
The ceramic heater and welder's blanket protected my system during the freeze and I didn't have to worry about anything catching fire.
The Physics of Freezing and Freeze Protection
Recently, there have been a lot of questions from those living in moderate climates about using automatic freeze protection or running pumps to prevent freezing and what a pool owner should do when temperatures drop so I thought it might be useful to have a thread which dealt with the issue from...

Mostly I just extend run times and for overnight temps down to the lower 20's I use a moving blanket and a (getting harder to find) incandescent light bulb.
Several years ago I learned the limits of this approach during a long, deep freeze. My flowmeter and the pressure gauge on my filter, which stick out from the plumbing and have little or no water flowing through them, both froze and had to be replaced.
With an extended hard freeze in the forecast I wanted to use a small ceramic forced-air heater to protect these parts of my system, but I was concerned about flammability of the moving blanket. While perusing Amazon I ran across fireproof, insulating, fiberglass welder's blankets, which are available in a variety of sizes.
The ceramic heater and welder's blanket protected my system during the freeze and I didn't have to worry about anything catching fire.