BloomWatch

Blue-green algae risk for dog owners

Is your lake safe for your dog?

Long-term bloom & toxin risk for 145 popular U.S. lakes, plus weekly satellite checks for 134 of them, from EPA data, and state advisories in California, Oregon, Washington. Check before you go — then look at the water when you get there.

Showing all 145 lakes · satellite data as of Nov 13

Higher risk
Model predicts elevated bloom & toxin risk, especially in warm months.
Moderate risk
Some predicted risk. Blooms come and go — check each visit.
Lower risk
Lower predicted odds — not zero. Still look before they swim.

At the water’s edge

A 30-second check before your dog goes in

  1. 01LookGreen paint, pea-soup color, scum, mats or foam — especially along the shore and in calm coves.
  2. 02Check for signsPosted advisories, dead fish, or a musty, rotten smell are all red flags.
  3. 03When in doubt, stay outKeep them leashed, bring fresh water to drink, and rinse them off after any swim.

If your dog was in suspicious water

Signs of algae poisoning & what to do

Watch for

  • Vomiting, diarrhea or heavy drooling
  • Weakness, stumbling or collapse
  • Trouble breathing, tremors or seizures
  • Pale gums, not eating, dark urine (can show up hours to days later)

Act fast

  1. Rinse your dog with clean water — wear gloves.
  2. Don’t let them lick their fur or drink more.
  3. Call your vet or nearest emergency vet now. Symptoms can start within minutes.
  4. If you can, photograph the water and note where they swam.

ASPCA Animal Poison Control (24/7, fee may apply): (888) 426-4435

Good to know

Common questions

What does a toxic algae bloom look like?

Water that looks like pea soup or spilled green paint, floating scum or mats, blue-green or brownish streaks near shore, or foam. It may smell musty or rotten. Toxins can also be present when the water looks clear, which is why risk matters.

Why are dogs at higher risk than people?

Dogs swim through scum, drink lake water, and lick it off their fur afterward, so they swallow far more than a person would. Some cyanobacteria toxins can kill a dog within hours.

When are blooms most likely?

Mostly in warm, sunny, calm weather, especially late summer into early fall, and in shallow, slow-moving or nutrient-rich water. Wind can push scum into a single cove, so conditions vary across the same lake.

Does “lower risk” mean the lake is safe?

No. It means the model predicts lower odds for that lake overall. A bloom can still form, so look at the water every visit.

Is this live data?

Partly. The risk level is a long-term prediction from EPA research on each lake’s watershed. The satellite check is recent: EPA’s CyAN program measures cyanobacteria from space, and we show its newest clear daily image (usually a day or two old) next to the weekly composite. It can’t see through clouds, and its 300-meter pixels miss shoreline scum, small coves and small lakes. For California, Oregon and Washington we also show the state’s own advisories and bloom reports, which come from testing and sightings at beaches and shorelines. Most lakes aren’t tested every week, so no advisory isn’t an all-clear. Nothing here replaces looking at the water.