A temperature warning system for a vehicle includes a thermal plug disposed on the wheel end assembly of the vehicle. The thermal plug is in fluid communication with an air supply and with a flow sensor. The flow sensor is operatively connected to a warning light or indicator. Excessive heat in the axle spindle end and/or the wheel end assembly causes a fusible material in the thermal plug to melt allowing air to flow from the air supply through the thermal plug thus activating the flow sensor. The flow sensor in turn activates the warning light or indicator alerting the driver of the vehicle of a problem condition at the wheel end assembly and/or axle spindle.