An unusual monsoon pattern has increased the chance for rare July thunderstorms in the Southland. Meteorologists say the biggest concern is dry lightning starting a fire, but there's also a chance for flash flooding and debris flows.

San Bernardino, Mohave and Clark counties were placed under an updated flood advisory by the National Weather Service on Thursday at 2:41 a.m. The advisory is in effect until 4:45 a.m.