Costa Mesa police are urging residents interested in receiving countywide alerts to register cell phone and alternate phone numbers with the area's mass notification system.

Residents registered with AlertOC will receive a test call from the system at 10 a.m. Sept. 20, according to an announcement from the Costa Mesa Police Department.

The test alert will replicate a large-scale emergency in conjunction with National Preparedness Month, and include 24 cities and unincorporated area from across the county, the announcement said.

Residents can register their cell phone number or email addresses at http://www.alertOC.com.

"Emergencies can happen at any time," the announcement stated. "A wildfire could spread or a flood could close the roads to a neighborhood while residents are away from home. In these instances, AlertOC is a critical link for residents to immediately learn of any required actions."

— Lauren Williams

Twitter: @lawilliams30