Riverside County firefighters responded to West Hays and North 12th Streets just before 1 p.m.
They said at least seven buildings, including houses, burned, along with a shed and a vehicle, before firefighters contained the flames.
Thirteen adults and six children were displaced, according to Cal Fire.
Neighbors hosed down their rooftops and trees to prevent the flames from spreading.
One person was seriously hurt and a firefighter suffered some minor injuries.
The cause of the fire is under investigation.