Although healthy algae is an important part of aquatic ecosystems, the right conditions can promote the growth of dangerous types of algae.

These harmful algal [AL-gull] blooms are most likely to occur during warm weather — even into fall. However, they can crop up at any time of the year. Other ideal conditions include low water levels and slow-flowing water.

Harmful algal blooms produce toxins that can seriously sicken — and even kill — animals and people who come into contact with contaminated food or water. There’s no way to tell if an algal bloom is harmful just by its appearance, so it’s important to stay on top of public health announcements. Still, if you’re concerned about the smell or appearance of algae on the water, it’s best to steer clear — and keep animals away, too.