https://dphhs.mt.gov/publichealth/Epidemiology/hab/
"These are public reports of algal blooms. Reports do not represent a comprehensive list of all HABs. Therefore, this map does not show the full potential of waterbodies experiencing blooms, nor can we accurately know the health risk at any given time. Advisories (caution or closure) are issued by experts, but it is impossible to keep the status of each report perfectly up to date. Toxin production may occur or dissipate at any moment. Please use your best judgment to determine if a bloom is in the area, andĀ if in doubt, stay out."