But since December 2019, they've been silent because of a cyber security threat.
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"We used to blow them at noon every Tuesday. I miss hearing them," said San Francisco resident Dan Clearwater.
If you don't believe a cyber attack is possible, here's what happened in Dallas a few years ago.
All of their sirens went off just before midnight on a Friday and lasted for 40 long minutes. 911 was flooded with calls from confused and scared residents.
EXCLUSIVE: San Francisco finds funding for emergency sirens; could be back as early as next year
"So then you go to worst case scenario, 'What's happening? Do I need to wake my kids up? Do I need to gather my things? What's happening?'" recalls a Dallas resident.
That was a wake-up call for San Francisco, which acknowledged that at any time, a hacker could potentially get ahold of its frequencies and codes.
Mayor London Breed addressed the issue at City Hall during a Disaster Council special meeting six months ago.
"We unfortunately had people who had access to the system who could use it for the wrong reasons," Breed said.
So San Francisco has been working to deliver a new state-of-the-art system.
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Except that, the city eventually determined that it didn't really have the money to upgrade the entire system.
Then came the Maui fire. While the siren system there was online, the head of the Emergency Management Agency decided not to sound the alarm, for fear it would confuse people into thinking it was a tsunami warning and people would run uphill toward the fire. One hundred and one people died.
It left San Francisco wondering, what if the city had a disaster?
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With the siren system "offline," the city has no back up emergency alert system.
Instead, in January 2022 the city's first responders had to physically go out to Ocean Beach with a loud speaker to alert residents that a tsunami warning was in effect because the sirens were offline.
MORE: All 119 San Francisco sirens are going silent -- for now
We asked San Francisco resident Nick Bardy how he would be notified in the event of a tsunami warning.
"I guess we wouldn't know if it's off. Maybe our phone would go off. I hope so," Bardy said.
Sure, 195,000 people receive text messages through AlertSF on their phones, but more than 800,000 people live in San Francisco, and that doesn't include all the people who work there or visit the city. Mobile phones may not be the best way to reach people in a disaster. On Thursday, AT&T had a nationwide outage, so none of their subscribers would have been able to receive any kind of warning on AlertSF.
Neal Humphrey is with Deepwatch, a cybersecurity company. He says the AT&T outage is a good example that a back up system is crucial.
"You have a physical back up system that has been in place for a number of years. It has the ability to do things over and beyond what current technology can do. If it ain't broke don't fix it," Humphrey said.
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"I think it's way past due, and I don't know how long before they work," Clearwater said.
Apparently neither does the city. Here's what the head of the Department of Emergency Management promised in that meeting six months ago.
"I think we expect in the next six months that the project will be well on its way," said Executive Director Mary Ellen Carroll.
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Yet, here we are in February 2024 with nothing to report.
Here's what we know.
The San Francisco Department of Technology did an assessment and determined that "most of the equipment was non-functional."
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We wanted more information and went to their offices and found the doors locked.
Instead, they referred us back to the Department of Emergency Management.
They, too, did not want to talk to us, sending us an email instead.
In a statement Emergency Management said, "Once funding is identified, the city will determine the most streamlined and cost-effective way to procure a solution."
The first phase of the project called for replacing 27 sirens along the beach shoreline. A year ago that would have cost them $5 million but now the price has gone up to $7 million.
In order to replace the entire network, all 119 of them, the total estimated price is now $20 million. That's roughly $168,000 per siren.
"You want to get the best technology, you want it to be durable, you want it to be long lasting. It's an investment worth making, but at this point we don't even have a plan," said Supervisor Aaron Peskin.