Don’t be alarmed when West Valley nuclear plant tests emergency sirens

PHOENIX – Every year, the Palo Verde Nuclear Generating Station is required to test its emergency notification system, including sirens and cellphone alerts.

The testing for 2025 is set for midday Thursday.

On 12/4, Palo Verde Generating Station and local/state agencies will test outdoor warning sirens within 10 miles of the station. Sirens will sound at 12 p.m. & 12:30 p.m. An opt-in Wireless Emergency Alert will go out at 12:15 p.m. More info: https://t.co/3hWesTZVGf. pic.twitter.com/B0CZv7wtg3

— Maricopa County Dept of Emergency Mgmt (@MaricopaReady) December 3, 2025

It will cover sirens within a 10-mile radius of the power plant at Baseline and Wintersburg roads in Tonapah, about 55 miles west of downtown Phoenix.

The sirens will blare twice for about three minutes — at noon and again at 12:30 p.m. — according to Maricopa County Emergency Management.

The process will also trigger a Wireless Emergency Alert at 12:15 p.m. for cellphones within the siren test area that are opted in for test alerts. The message will say: “This is a test of Maricopa County Wireless Emergency Alert system. No action is required.”

In the unlikely event that an actual emergency occurs at the plant at the same time the tests are scheduled, alerts directing people to tune to their TVs or radios for more instructions would be sent.

Why do Palo Verde plant sirens have to be tested?

Palo Verde is the second largest nuclear plant in the United States, generating enough electricity to power more than 4 million homes and businesses.

Arizona Public Service operates the facility, which produces electricity for parts of Arizona and several other states.

The siren testing is required by the Nuclear Regulatory Commission and the Federal Emergency Management Agency.

More information about emergency preparedness in metro Phoenix can be found at the Maricopa County Emergency Management website.

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