Complex sentence: The rains poured down for much of the day Thursday, Aug.18, starting at about 3 a.m. By 11 p.m., the Shepaug River and brooks in the western portion of the state had begun to overflow their banks.
Split into simpler sentences: The rains poured down for much of the day Thursday, August 18, starting at about 3:00 AM. By 11:00 PM, the Shepaug River and brooks in the western portion of the state had begun to overflow their banks.