Upper Klamath Lake algae bloom status

Upper Klamath Lake algae bloom history

The Oregon Health Authority has issued 19 advisories and precautions for Upper Klamath Lake since 2015, covering 10 of the 11 years from 2015 to 2025.

19 were recreational use health advisories, issued when toxins or cyanobacteria are above Oregon's guideline values for people.

Reports have fallen in the last three years compared with the three before.

That puts Upper Klamath Lake 2nd of the 30 Oregon lakes on this site for the number of years with blooms.

Recent Upper Klamath Lake algae reports

What the Oregon results mean

The Oregon Health Authority issues two kinds of notice for waterbodies it monitors.

Health advisory

Toxins or cyanobacteria are above Oregon's recreational guideline values for people. Avoid swimming and water activities that could make you swallow water, and keep pets and children out.

Precaution

Toxins are below the guidelines for people but still above Oregon's guideline values for dogs. Keep pets away from blooms and avoid foamy, scummy or paint-like water.

Is Upper Klamath Lake safe for dogs?

Dogs are at the greatest risk from toxic algae. They swallow water while swimming, eat scum on the shore and lick algae off their fur afterwards, and a small amount can kill a dog within hours. With blooms recorded in 10 different years here, take particular care at Upper Klamath Lake.

• Keep your dog on a lead near water that looks green, scummy, foamy or discoloured, and away from algae washed up on the shore.
• If your dog gets in, rinse it straight away with clean water and don't let it lick its coat.
• Call a vet immediately if your dog vomits, drools, has diarrhoea, staggers, shakes or seems weak after being near the water.

Read the full guide to toxic algae and dogs: symptoms, what to do in the first minutes and how vets treat it.

Health effects of toxic algae

Blue-green algae (cyanobacteria) can produce toxins that affect the liver, nervous system and skin. Swallowing water during a bloom can cause stomach pain, vomiting and diarrhoea. Skin contact can cause rashes, and breathing spray from the water can irritate the eyes, nose and throat. Children are at higher risk because they are smaller and more likely to swallow water.

How to spot a bloom

Toxic blooms can look like pea soup, spilled paint or green streaks on the surface, and they can also be blue, brown, white or red. Scum often collects along the shore downwind. If you can't see your feet in knee-deep water, or you aren't sure, stay out.

Don't drink untreated lake water, and don't boil it to make it safe: boiling doesn't destroy algal toxins. If you feel unwell after contact with the water, contact a doctor or Poison Control on 1-800-222-1222.

Nearby lakes with algae reports

• Agency Lake17 km away, 3 reports, last in 2023
• Fish Lake37 km away, 3 reports, last in 2011

All Klamath County lakes with algae reports

Questions about Upper Klamath Lake

Is there algae in Upper Klamath Lake right now?

Oregon issued a health advisory for Upper Klamath Lake in 2025, listed on 23 December 2025. Oregon publishes its data once a year, so for today's conditions check the OHA current advisories page and the signs at the shore.

When was the last algae bloom at Upper Klamath Lake?

The most recent entry in Oregon's data is from 23 December 2025 at Microcystin, 8.19 ug/L: a health advisory.

Has Upper Klamath Lake had toxic algae before?

Yes. Blooms are recorded in 10 of the 11 years from 2015 to 2025.

Can dogs swim in Upper Klamath Lake?

Keep dogs out of the water whenever a bloom is reported or the water looks green, scummy or discoloured. Dogs are the animals most often killed by algal toxins because they swallow water and lick their fur. If your dog swims in water that might have algae, rinse it with clean water and call a vet if it vomits, drools, staggers or seems weak.

Can you eat fish caught in Upper Klamath Lake during a bloom?

If you keep fish caught during a bloom, health agencies advise removing the guts and liver and rinsing the fillets in clean water before cooking, because toxins collect most in the organs. Some agencies advise not eating fish from an active bloom at all, so follow local guidance.