PORTLAND, Maine (NEWS CENTER) — King tides come about once or maybe twice a year, bringing waters even higher than your typical high tide. This weather phenomenon brings the threat of serious flooding throughout lower parts of coastal towns, including in Portland.

King tides are regular occurrences, but these unusually high tides, experts say, act as predictors of how high future tides could be in the years to come, and they show the community how we need to prepare for those weather changes.

“What they're showing is what the normal high tide is going to look like in the future,” said USM art professor Jan Piribeck, a local king tide enthusiast.

This year's king tide will arrive Tuesday morning with waters expected to be as high as 12 feet — the highest since 1999 — which will cause flooding throughout lower parts of the land.

King tides affect not only pedestrians and drivers, but have negative economic impacts, too

“You know, the city [of Portland] is very concerned," Piribeck said. "The citizens are very concerned about the impact of these waters in Bayside and East Bayside."

Activists and enthusiasts fear that the height of the ocean — which has risen almost two inches in just the last two decades, combined with king tide flooding — could cause businesses along the coast to suffer.

“When you have a high of tide that is increased by an inch or so, it means that that tide goes inland, sometimes several feet and sometimes several miles,” Friends of Casco Bay employee Peter Milholland said.

The king tide for Portland is expected Tuesday at 10:56 a.m.