At 2:18 p.m. today, cell phones across the Berkshires & the United States will go off with a very distinct ring of an emergency presidential alert.

This will be the first nationwide test of a wireless emergency alert system, designed to warn people of a dire threat, like a terror attack, pandemic or natural disaster. There is no opting out, which has already prompted a lawsuit.

“THIS IS A TEST of the National Wireless Emergency Alert System,” it will read. “No action is needed.”

Two minutes later, radio stations, including WUPE will run EAS tests alerts over the air. Televisions will show test alerts.

According to Boston.com, officials say they believe that the wireless test will reach about 75 percent of the cell phones in the country, though they hope the number is higher. It could take up to 30 minutes for the alerts to be transmitted to all devices.

Some things that could interfere: ongoing phone calls or data transmission, a device that is turned off or out of range, and smaller cell phone providers that are not participating in the program.