As many as eight separate grass fires broke out near the 5 Freeway north of Castaic early Thursday, forcing an hours-long lane closure through the morning commute.

The California Highway Patrol reported that the fires began in the area before 4 a.m., forcing officials to issue a SigAlert and close the far right lane of the northbound 5 Freeway.

The first fire was reported around 3:30 a.m. between the Templin Highway and Smoky Bear Road, CHP Officer Christian Cracraft said.

The lane remained closed through 8 a.m. as crews mopped up the burn area, which reportedly totaled about an acre. The cause of the fires remained under investigation.


Meanwhile, scorching temperatures continue to batter the Southland, with highs expected to eclipse 100 degrees in the inland valleys.

Thursday will be one of the warmest days of the week, with Woodland Hills likely hitting 104, National Weather Service specialist Stuart Seto said.

Across Los Angeles County, temperatures were about eight degrees above normal.

“It’s definitely warm, but not record-setting,” Seto said.


County health officials have declared a heat alert for the Pomona area, where temperatures were in the upper 90s, through Friday.

Some relief should come Sunday, when temperatures are expected to drop five to seven degrees as clouds move into the area. The forecast even calls for a slight chance of thunderstorms for the San Gabriel Mountain areas, Seto said.

Follow @MattStevensLAT for Westside coverage and breaking news.