SF's noon warning siren will shut down for next 2 years

The San Francisco sirens that go off every Tuesday at noon will be taking a two-year hiatus. The San Francisco sirens that go off every Tuesday at noon will be taking a two-year hiatus. Photo: PM Images, Getty Images Photo: PM Images, Getty Images Image 1 of / 3 Caption Close SF's noon warning siren will shut down for next 2 years 1 / 3 Back to Gallery

Tuesdays at noon will get a little quieter in San Francisco. If you're not familiar with the Outdoor Public Warning System, it's that jarring siren that goes off every week at the same time, followed by a low voice saying, "This is a test."

San Francisco's Department of Emergency Management announced today that the alarm system will be going out of service during a two-year upgrade project. The upgrades, which are estimated to cost between $2 million and $2.5 million, will improve the reliability and security of the siren system. This means the installation of a new operating system, and stronger encryption and hardware.

RELATED: Everything you ever wanted to know about San Francisco's noon siren

The first 50 sirens were installed in San Francisco in 1942 to warn of World War II air raids. Currently, there are 119 sirens, which are designed to alert residents about critical emergencies such as a tsunami, contaminated water supply or radiological attack. However, they have only been used in a real emergency once: in 2012, sirens alerted Treasure Island residents to water contamination due to a water main break.

On Wed., Dec.11, the @SFCityCIO will temporarily shut down the Outdoor Public Warning System for the next two years to update its operating system and strengthen encryption. To receive AlertSF emergency texts, text your zip code to 888-777. For more info: https://t.co/6jH1RVx0iH pic.twitter.com/DL9U5Us8kU — San Francisco DEM (@SF_emergency) December 3, 2019

The last siren test will occur Dec.10 at noon. During the upgrade, San Franciscans can receive emergency text messages about natural disasters, major police, fire, health emergencies, or significant transportation disruptions by signing up for AlertSF (just text your zip code to 888-777 or visit www.alertsf.org to register).

Correction: A previous version of this article stated that the sirens had never been used in a real emergency before.

Madeline Wells is an SFGATE associate digital reporter. Email: madeline.wells@sfgate.com | Twitter: @madwells22