GUERNEVILLE, Calif. - Mid- and late summer is the time when algae blooms appear, bringing the threat of toxicity to families hoping to enjoy the water.
That's going on right now in Sonoma County, where there are good algae and toxic algae.
It's important to know the difference as the summer gets hotter and the algae blooms get bigger.
Warning signs are posted along the Russian River at 10 beaches. They warn about potentially toxic algae sighted from near Healdsburg to the lower Russian River.
The algae, which can spread toxins into the water, is usually found in floating patches called mats, of brown, orange, olive or dark red. It can also get stranded on rocks or on the bottom spread toxic into the water. It can be particularly harmful to small children and dogs.
The Williams family was hanging out at the popular Sunset Beach on Thursday.
"I heard about it last night," Rhonda Williams said. "I went home and looked it up on the internet and then we saw the signs today."
Nonetheless, the Williams family checked it out.
"We had a good time and Mica did go into the water and so did the dog and they were fine. There's not any algae pads down there. So you just really have to watch what you're doing and we did look," said Williams.
It is as much and economic threat as a threat to health.
The biggest threat is in Guerneville at Johnson Beach.
This is not only a place for locals, but for people from the Bay Area, the greater California communities as well as people from all over the country.
Jackie Marshall has two homes back east, one in New York.
"I have a house in Florida. It is a big concern. There is toxic algae. So yes, it is a concern. But, in Northern California, I would image where you're so ecologically aware, it should be a big concern," said Marshall.
One young man from Petaluma showed no fear.
"I'm out here and I'm gonna enjoy the river. I mean, I've been enjoying the river all my life. It's just a little bit of algae. Yeah, I could get sick, but it's not the end of the world," said Stephen Allen.
Toxic algae has also been found in Santa Rosa's Spring Lake.
The North Coast Regional Water Quality Control advises visitors, especially boaters, fishermen and women, to be cautious.
Though swimming and wading are not allowed, Spring Lake Regional Park's swimming lagoon, which his treated to prevent algae, is open and safe.