What revision should be made to maintain parallel structure?

Sentence 1 should be revised to read, “Outside the snow fell; inside the heater came on with a distant roar.”
Sentence 2 should be revised to read, “Outside, the wind howled through the big oak; inside, a log snapped in the fireplace.”
Sentence 3 should be revised to read, “Outside, footsteps walked hurriedly past the window; inside, the cat stretched and purred.”
Sentence 4 should be revised to read, “In the night, an owl hooted; in the room, a page turned.”