Lake · Larimer County · CO
Is Boyd Lake safe to swim?
No advisory or algae bloom reported for this water today.
Updated July 20, 2026 · EPA CyAN satellite
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What's in the water at Boyd Lake right now
As of July 20, 2026, Boyd Lake in Larimer County, Colorado is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Rainfall over the past week totaled 0.0 in, which can wash bacteria and nutrients into the water.
Blue-green algae at Boyd Lake
Boyd Lake is a lake in Larimer County, Colorado covering about 2.5 sq mi, the 23rd-largest of the 107 lakes SwimZone monitors in Colorado. Satellite imagery detected no blue-green algae bloom as of July 19, 2026.
Blue-green algae (cyanobacteria) blooms are most common from midsummer into early fall, when the water is warm, calm, and rich in nutrients from runoff. They can produce toxins that make people sick and can be rapidly fatal to dogs, so skip water that looks green, scummy, or like spilled paint, and keep children and pets out of it.
Bloom history at Boyd Lake
From EPA CyAN's satellite archive
Over 7 summers of satellite monitoring since 2020, Boyd Lake has reached blue-green algae advisory levels in 2 of them, most recently in August 2024. Blooms here have been occasional rather than annual. Its highest recorded reading was 325,944 cells/mL in August 2024.
Frequently asked: swimming in Boyd Lake
- Is it safe to swim in Boyd Lake right now?
- Boyd Lake is clear to swim today. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.
- Does Boyd Lake have blue-green algae (cyanobacteria)?
- No blue-green algae bloom is detectable at Boyd Lake as of July 19, 2026 (below the satellite's roughly 10,000 cells/mL detection limit). Cyanobacteria can still appear within hours in warm, calm, nutrient-rich water, so look before you swim.
- Can dogs swim in Boyd Lake?
- No bloom is detected at Boyd Lake today, but dogs are much more vulnerable to blue-green algae than people, and blooms can form within hours. Always keep dogs away from water that looks green, scummy, or discolored, and rinse them off after swimming.
- How often does Boyd Lake have blue-green algae blooms?
- Over 7 summers of satellite monitoring since 2020, Boyd Lake has reached blue-green algae advisory levels in 2 of them, most recently in August 2024. Blooms here have been occasional rather than annual. Its highest recorded reading was 325,944 cells/mL in August 2024.
- How many Colorado lakes and beaches are unsafe for swimming today?
- Today, 26 Colorado waters are above a safe-contact threshold and 3 more warrant caution, out of 113 monitored waters SwimZone tracks in the state.
- How is Boyd Lake's water quality measured?
- SwimZone builds this read from EPA CyAN satellite imagery for blue-green algae, official beach and fecal-bacteria advisories where a program monitors Boyd Lake, and a recent-rainfall overlay, all refreshed daily. It was last updated July 20, 2026.