I guess it was Sluggo. I let him cool down for twenty minutes, and everything is back to normal. Maybe another defrag is in order.
Last time I went outdoors, while Sluggo was resting, it had begun to sprinkle, and I heard the frogs croaking happily, and the hooves of deer down at the corner by the orchard. Rather than hang about in front of this screen, I'm going to go back out and enjoy the rest of the night.