Sea level rise is threatening coastal cities around the world.

If you live in a city like Miami, New York City, or Charleston, the evidence is apparent if you head to the right neighborhood during high tides — especially those known as king tides. These are the highest tides of the year, and they coincide with full moons during spring and fall.

King tides themselves aren't caused by sea level rise, but as the highest tides of the year, they show how sea level has already risen over the past century — the neighborhoods they flood on sunny days now didn't flood like this decades ago, even during high tides.

In 2017, the National Oceanic and Atmospheric Administration (NOAA) found that cities around the country experienced a record number of flooding events related to high tides, according to the National Climate Report. More than a quarter of coastal locations tied or set new records for the number of flooding days. And in 2018, flooding on the US coastline is expected to be 60% higher than it was just 20 years ago.

Perhaps most importantly, high and king tides are a preview of what's to come as seas continue to rise. What happens during high tides now will happen on a regular basis in the future.

As sea level rises, waters come back up through storm drains and wash over barricades. They flood houses and roads. And in many cases, they may be full of bacteria and potential pathogens.

Most cities recognize the situation at this point and are doing everything they can to try to beat back the rising tides. But seas will continue to rise as warmer oceans expand and glaciers melt. It's likely that neighborhoods and even some cities will be uninhabitable far sooner than many think.