New Croton Reservoir algae bloom history
New York's Department of Environmental Conservation listed New Croton Reservoir as having a harmful algal bloom in 4 of the 10 years from 2016 to 2025.
Blooms were confirmed by state staff in 1 year; in the other years they were reported as suspicious but not confirmed.
- 2016 Suspicious, 1 report
- 2017 Suspicious, 1 report
- 2018 Suspicious, 1 report
- 2019 None
- 2020 None
- 2021 None
- 2022 None
- 2023 None
- 2024 None
- 2025 Confirmed, 1 report
When do algae blooms happen at New Croton Reservoir?
At New Croton Reservoir, reports are most often logged in August and September.
About 100% of reports fall between May and September, when warm, calm, sunny weather lets blue-green algae multiply.
Blooms can appear, move with the wind and fade within hours or days, so the time of year is only a guide.
Recent New Croton Reservoir algae reports
New York publishes one entry per lake for each season it appears on the bloom list, showing when it was first and last listed and its highest status.
| Date | Result |
|---|---|
| 11 August 2025 | Confirmed bloom |
| 24 August 2018 to 13 October 2018 | Suspicious bloom |
| 22 September 2017 to 27 October 2017 | Suspicious bloom |
| 26 August 2016 to 2 October 2016 | Suspicious bloom |
What the New York results mean
New York sorts each bloom by how far it has been checked.
- Suspicious bloom
- Reported to the state but not yet confirmed as blue-green algae.
- Confirmed bloom
- State staff confirmed blue-green algae from photos or a sample. Avoid contact where the bloom is.
- High toxins
- Toxin levels high enough to be a health concern. Recorded separately from 2012 to 2018.
Is New Croton Reservoir 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 4 different years here, take particular care at New Croton Reservoir in August and September.
- 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.
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
- Lake Mohegan9 km away, 12 reports, last in 2025
- Muscoot Reservoir10 km away, 3 reports, last in 2025
- Bedford Lake11 km away, 9 reports, last in 2022
- Lake Peekskill12 km away, 10 reports, last in 2025
- Barger Pond13 km away, 10 reports, last in 2025
Questions about New Croton Reservoir
Is there algae in New Croton Reservoir right now?
New Croton Reservoir was on New York's harmful algal bloom list on 11 August 2025, with confirmed bloom status (1 report). New York publishes its data once a year, so for today's conditions check the NYHABS map and the signs at the shore.
When was the last algae bloom at New Croton Reservoir?
The most recent entry in New York's data is from 11 August 2025: a confirmed bloom.
Has New Croton Reservoir had toxic algae before?
Yes. Blooms are recorded in 4 of the 10 years from 2016 to 2025, most often in August and September.
Can dogs swim in New Croton Reservoir?
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 New Croton Reservoir 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.
About this data
This page uses official records from the New York State Department of Environmental Conservation (DEC), which published as a yearly summary; the current season is shown on the NYHABS map. Reports are grouped by waterbody. The site was last rebuilt on 24 October 2026.
States only test some lakes, some of the time, so a lake without a recent report hasn't necessarily been checked. This page is independent, isn't affiliated with the State of New York, and isn't health advice. View the source data.