How does he know?

Owen is terrified of thunder. One of the only things he's afraid of really. Two nights ago. After I turned off the light, but before I was asleep, Owen jumped up and stood on the bed. He looked at his kennel. He whined. He stared. I assumed he was gonna get sick. Instead he jumped down, went into his kennel and waited. About 3-5 minutes later it started thundering like crazy. After the last one (how did he know?) he jumped back up on the bed and went to sleep.

Last night, same thing. He got up. stared, waited a minute or two, got in his kennel, and then a few minutes later it started thundering.

Now, aside from a little game with treats thunder the ONLY time he goes in the kennel. How does he know? Barometer? Super hearing?