A “boil water” advisory is a public notice that a public utility’s water supply has become unsafe to consume, and you should boil tap water (and let it cool) before using it. There are many different reasons this could be the case, including E. coli contamination, elevated levels of lead, or other contaminants that enter the water supply after a water main bursts. (There are about 260,000 of these “breaks” every year in the U.S. or Canada, according to the American Society of Civil Engineers. That’s about one every 2 minutes.)

When drinking, cooking, or brushing your teeth with your tap water is unsafe, it might take several days for local officials to notify you. You might get a phone call or a knock on your door. You might also be expected to find out about it from a local news outlet. The utility that provides your tap water, not any government agency, issues these alerts.

Most major media news outlets do a good job of reporting them, the same way they do with tornado or flash flood warnings from the National Weather Service. Here’s a list of just some of them. Want to see how often your water supply raises a red flag? Click here to find out.