With parts of Los Angeles County still smoldering from wildfires, the expected rain this weekend would seem like a welcome relief. But how the rain falls could make the difference between a disaster respite or a disaster repeat.

Two fires erupted in the San Diego area on Thursday afternoon, prompting evacuations. The Border 2 Fire, which broke out in the Otay Mountain Wilderness area east of Chula Vista and north of the U.S.-Mexico border, has burned approximately 4,250 acres, according to the California Department of Forestry and Fire Protection.

The blazes - named Laguna, Sepulveda, Gibbel, Gilman and Border 2 - flared up on Thursday in Los Angeles, San Diego, Ventura and Riverside.