A warm Minnesota summer day – time to hit the water.

“Like tiny weeds, small blades of grass or something,” says 11-year-old Hayden Priest.

At Lake Nokomis Main Beach, Priest and his friends made an unpleasant discovery.

“I’ve been seeing lots of algae, like blue and green algae,” he declares. “It doesn’t feel like anything really, it’s just kind of gross, and bad for pets and people. I read the sign.”

That sign, from the Minneapolis Park and Recreation Board, is warning beach goers about a hazardous algae discovery.  

RELATED: Blue-green algae alert issued for Lake Nokomis

“If in doubt, best to keep out, is really the best advice we always give to individuals,” notes Trisha Robinson, the supervisor of the Waterborne Diseases Unit at the Minnesota Department of Health.

Robinson says blue-green algae that may look like green paint or pea soup, is a kind of bacteria. The strain is called cyanobacteria and can sometimes release a toxin that can make you or your pets, especially dogs, very sick.  

“If they go into the water, or ingest the water, or breathe in the water,” Robinson explains. “If somebody gets it on them, they might get a rash, if somebody is inhaling it, they might get respiratory symptoms.”

She says the bacteria can cause vomiting or diarrhea in people.

But in dogs, it can trigger respiratory problems- and can even be fatal.

Experts say part of the problem is that dogs typically ingest water while swimming or playing, and often lick their fur after getting out.

But we wondered, why are blooms like this appearing now?

The Friends of the Mississippi River say hotter weather helps the bacteria to grow and spread.

Andrew Andestic, from St. Paul, says he’s encountered this before, spending summers in Wisconsin.

“One year, a bunch of people got rashes. We’ve always been careful,” he notes. “I’m glad they put the advisories up, because we have kids and if they were little, we wouldn’t want them swimming in there.”

The Park and Recreation Board says the Lake Nokomis Main Beach is the only one that’s been affected by the bacteria so far.  

On Thursday afternoon, the beach crowd here was evenly divided, with some going in and others not.

Brittany Priest, Hayden’s mother, says she’s trying to strike a balance- wanting her kids to have fun, but also take precautions.

“Told the kids to keep their mouths closed when they swim and make sure they don’t inhale anything,” she explains. “We’ll make sure they rinse off when they’re done swimming. I think tomorrow, we’re going to head out to the suburbs and go for one that doesn’t have as much algae in it, where the risk isn’t there.”