The Freeze Miser™ operates like the thermostat in your home. It senses the internal water temperature arriving to the faucet not the air temperature. It can be 40º F or -40º F, it does not care. The Freeze Miser™ activates when the water temperature hits 37º F. No water is allowed to drip until the activation temperature is attained. As the water temperature fluctuates, so does the drip. The Freeze Miser™ is on guard 24/7