By Anna Giles

SACRAMENTO (CBS13) – Hot temperatures have many headed straight to local waterways to cool off, but experts say high heat and a bad drought this year can be ideal conditions for harmful algae.

It’s an issue that’s not always top of mind.

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“I wouldn’t even think to check for algae, but maybe if the water does look dirty, that would be the only reason to check or even know it could be an issue,” said Sacramento resident Triston Chirgwin.

According to state data, popular waterways in the immediate Sacramento area are safe. People headed to the American River or Folsom Lake for the Fourth of July are in the clear.

But the state labels part of Discovery Bay near San Francisco as a danger area, with a warning not to swim or touch the scum on the water. Other Bay Area waterways have the same warning, including the Big Break Regional Shoreline.

Warning signs went up in some parts of Sacramento about potential harmful algae in stormwater quality flood control basins.

“It’s an occurrence that can happen when you have warm temperatures and water that doesn’t flow,” said Carlos Eliason with the Sacramento Utilities Department

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Eliason said people don’t swim in these basins, but they look like ponds where kids might play or people walk their dogs. People are now warned to not touch or ingest the scum in the water. And if you fish there, wash your catch really well.

Eliason said drought conditions indirectly make the problem worse.

“People are getting better at not wasting water and letting it go onto the sidewalks,” he said.

That means less water running off into these flood control basins.

“So when you have less water you have generally higher temperatures, it’s one of the conditions where these bacteria algae can form,” Eliason said.

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You can check for harmful algae at waterways all over the state by clicking here.