Cold causes headlights to come on and drain the battery

have an 03 vibe. when the temperature get cold around 18 degrees or colder, what would cause the daytime running lights to com on by thier self and drain the battery.

The lights are tied to power through a relay and the relay is controlled by the daytime running lamp control module. The module makes a ground connection on the relay coil to turn on the relay which then switches power to turn on the lights. The trouble is most likely coming from the module but it could be the relay. If disconnecting the plug to the module turns the lights out while the trouble is occuring then the module is at fault. If the lights stay on then the relay is the trouble.