Algae Bloom Advisories
Lakes most likely to develop blue-green algae (cyanobacteria) blooms in Minnesota and Wisconsin, based on chlorophyll-a measurements above 20 µg/L. These are bloom-prone waters — not necessarily active advisories.
For real-time current advisories, always check the state agencies directly:
Bloom-prone lakes in Minnesota
| Lake | Algae | Grade |
|---|---|---|
| Augusta Lake Dakota County | 160 µg/L | F |
| Hanska Lake Brown County | 99.6 µg/L | F |
| Allie Lake Renville County | 98.3 µg/L | F |
| George Lake Martin County | 93.5 µg/L | F |
| Typo Lake Anoka County | 88.1 µg/L | F |
| Hall Lake Martin County | 80.1 µg/L | F |
| Budd Lake Martin County | 75.8 µg/L | F |
| Clear Lake Brown County | 55.6 µg/L | F |
| Amber Lake Martin County | 53.4 µg/L | F |
| Center Lakedeep Cook County | 52.7 µg/L | D |
| North Stanchfield Lake Isanti County | 50.7 µg/L | F |
| Sisseton Lake Martin County | 49.1 µg/L | F |
| East Arctic Lake Scott County | 48.2 µg/L | F |
| Washington Lake Le Sueur County | 48.1 µg/L | F |
| Clear Lake 1 Goodhue County | 44.6 µg/L | D |
| Preston Lake Renville County | 44.1 µg/L | F |
| Goose Lake Goodhue County | 43.5 µg/L | D |
| Pioneer Lake Chisago County | 43 µg/L | F |
| Sleepy Eye Lake Brown County | 41.7 µg/L | D |
| Emily Lake Le Sueur County | 40.1 µg/L | F |
| Wellner-Hageman Reservoir Brown County | 38.5 µg/L | D |
| Gerhardt Lake Dakota County | 38 µg/L | D |
| South Stanchfield Lake Isanti County | 33.4 µg/L | F |
| Rush Lake Chisago County | 29.5 µg/L | D |
| Martin Lake Anoka County | 28.9 µg/L | D |
Bloom-prone lakes in Wisconsin
| Lake | Algae | Grade |
|---|---|---|
| Milwaukee Harbor South Half Lake Milwaukee County | 31 µg/L | D |
| Milwaukee Harbor Lake Milwaukee County | 26 µg/L | C |
| Milwaukee Harbor North Half Lake Milwaukee County | 26 µg/L | C |
| Milwaukee Harbor Lake Milwaukee County | 23 µg/L | D |
| Big Round Lake Polk County | 21 µg/L | C |
If you see a bloom
- Do not swim or let pets enter the water.
- Do not drink, cook with, or boil the water (boiling concentrates the toxins).
- Rinse off immediately with clean water if exposed.
- Report the bloom to MN PCA ([email protected]) or WI DNR.
- Watch dogs closely after lake exposure — symptoms can appear within 30-60 minutes.