A harness for heating and/or cooling a wearer (e.g., a pet) of the harness includes an outer cover including a harness neck strap and a harness chest strap for securing the harness about the wearer of the harness, an internal surface having a breathable fabric material, at least one sensor attached to the harness chest strap, a thermal control device that cools or heats the wearer of the harness, a controller to activate the thermal control device, and straps arranged over an external surface of the outer cover.
