It was more spectacular before I thought to grab the camera, of course.
I grew up hearing this called sheet lightning or heat lightning, but to be correct I think it's actually called intra-cloud lightning.
I didn't realize, until playing it back, how loudly the frogs out in the pond were singing. And inside, you can hear Beaker (our parakeet, aka budgie) squawking, whistling, and talking. At around 11-12 seconds he says, "crazy bird". You'll have to have your ears pricked and the sound turned up to hear it.