A grain loss sensor array system is provided for an agricultural harvester. At least one thermal sensing device is attached to a header of the agricultural harvester and captures infrared images or video of the ground. A controller detects pre-harvest loss and harvest loss using the infrared images or video by recognizing a temperature difference or a characteristic thermal difference between the pre-harvest loss, the harvest loss, and the ground. The controller may communicate with or be integrated with a yield monitor to provide information concerning the pre-harvest loss and harvest loss to an operator of the agricultural harvester.
