Simplify the following text for a Grade 14 native English-speaking person.
Original: In August 1935 , the remnants of an unnamed tropical storm that landed on Southern California caused torrential rain and flooding across Arizona , especially along the Santa Cruz River and Rillito Creek on Southern Arizona .
Simplified: In August of 1935 , the remnants of an unnamed tropical storm that landed on southern California causing heavy rains and flooding across Arizona , especially along the Santa Cruz River and Rillito Creek on Southern Arizona .