Springtime burning to clear agricultural fields is a common practice. The intense heat from these fires is detected using the GOES-8 shortwave infrared channel, resulting in some pixels appearing as dark "hot spots" on the image.
Notice how the larger lakes across Kansas and Nebraska appear as cooler (lighter gray) spots on the infrared image -- land surfaces heat up more rapidly than water surfaces (surface temperatures over land this day were in the 70's F).
