Safest Lakes to Swim In in Idaho
41 lakes in Idaho qualify as safest for swimming, all hold grade A or B and report chlorophyll-a (algae) under 10 µg/L. Always check local advisories on the day you swim.
Ranked List
| # | Lake | County | Grade | Clarity | Phosphorus | Algae |
|---|---|---|---|---|---|---|
| 1 | Nla Lake | Gem | A | 17.6 ft | 19.7 µg/L | 1.3 µg/L |
| 2 | Nla Lake | Valley | A | 18.6 ft | 10.2 µg/L | 0.7 µg/L |
| 3 | Nla Lake | Blaine | A | 29.9 ft | 14.6 µg/L | 0.7 µg/L |
| 4 | Nla Lake | Kootenai | A | 19.2 ft | 16 µg/L | 2.1 µg/L |
| 5 | Nla Lake | Shoshone | A | - | 9.9 µg/L | 1.2 µg/L |
| 6 | Nla Lake | Valley | A | - | 18.2 µg/L | 3.9 µg/L |
| 7 | Nla Lake | Custer | A | - | 17.7 µg/L | 1 µg/L |
| 8 | Deadwood Reservoir | Valley | A | 17.2 ft | 14 µg/L | 1.7 µg/L |
| 9 | Ririe Reservoir | Bonneville | A | - | 19 µg/L | 3.2 µg/L |
| 10 | Bear Lake Off North Beach | Bear Lake | A | 21.7 ft | 11 µg/L | - |
| 11 | Bear Lake | Bear Lake | A | 19 ft | 4.2 µg/L | 0.3 µg/L |
| 12 | Bear Lake Se of St Charles Replicate of | Bear Lake | A | 19 ft | 4.5 µg/L | 0.3 µg/L |
| 13 | Usgs Lake | Kootenai | A | - | 4 µg/L | 1.6 µg/L |
| 14 | Ideq Lake | Kootenai | A | - | 5 µg/L | 1.3 µg/L |
| 15 | Ideq Lake | Kootenai | A | - | 4 µg/L | 1 µg/L |
| 16 | Ideq Lake | Kootenai | A | - | 3.5 µg/L | 1 µg/L |
| 17 | Cat Creek Lake | Elmore | A | - | 17 µg/L | 4.4 µg/L |
| 18 | Nla Lake | Bonner | A | 11 ft | 6.6 µg/L | 2.5 µg/L |
| 19 | Pasisades Reservoir | Bonneville | A | 10.5 ft | 15 µg/L | 2.9 µg/L |
| 20 | Palisades Reservoir | Bonneville | A | 12.5 ft | 18 µg/L | 1.9 µg/L |
| 21 | Deadwood Res Off Face of Dam Lake | Valley | A | - | 25 µg/L | 2.3 µg/L |
| 22 | Nla Lake | Bonner | B | 6.9 ft | 12 µg/L | 2 µg/L |
| 23 | Palisades Lake | Bonneville | B | 13.1 ft | 20.5 µg/L | 2.1 µg/L |
| 24 | Lake Lowell | Canyon | B | 7.2 ft | 17.5 µg/L | 1.5 µg/L |
| 25 | Arrowrock Reservoir | Elmore | B | 12.5 ft | 35 µg/L | 1.5 µg/L |
| 26 | Nla Lake | Adams | B | 12.5 ft | 45.5 µg/L | 2.1 µg/L |
| 27 | Nla Lake | Owyhee | B | 10.8 ft | 41.6 µg/L | 3 µg/L |
| 28 | Nla Lake | Gooding | B | - | 35.8 µg/L | 1 µg/L |
| 29 | Black Cnyn Reservoir Ns of | Gem | B | 7.5 ft | 29.5 µg/L | 3.1 µg/L |
| 30 | Cascade Reservoir A Sugar Loaf Island | Valley | B | 8.5 ft | 28 µg/L | 1.1 µg/L |
| 31 | Nla Lake | Idaho | B | 19.2 ft | 53000 µg/L | 1.1 µg/L |
| 32 | Nla Lake | Bingham | B | 8.1 ft | 52.5 µg/L | 3 µg/L |
| 33 | Nla Lake | Washington | B | 15.1 ft | 41000 µg/L | 0.3 µg/L |
| 34 | Nla Lake | Boise | B | 23.3 ft | 23000 µg/L | 0.5 µg/L |
| 35 | Nla Lake | Shoshone | B | 22.1 ft | 37000 µg/L | 2.2 µg/L |
| 36 | Nla Lake | Custer | B | 38.1 ft | 9000 µg/L | 0.2 µg/L |
| 37 | Waha Reservoir Middle | Nez Perce | B | 9.7 ft | 45 µg/L | 3.9 µg/L |
| 38 | Cascade R W of Sugarloaf Island Lake | Valley | B | 8.2 ft | 28 µg/L | 8 µg/L |
| 39 | Cascade Reservoir | Valley | B | 8.2 ft | 31 µg/L | 1.1 µg/L |
| 40 | Lake Lowell Across From Upper Embankment | Canyon | B | 7.2 ft | 26 µg/L | 5.6 µg/L |
| 41 | American Falls R Lake | Bannock | B | - | 42 µg/L | 5.7 µg/L |