Pinellas-Seminole Lake
Pinellas-Seminole Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 1.5 ft visibility. Phosphorus: 63 µg/L.
- Clarity
- 1.5 ft
- Typical in September
- 85°F
- Type
- Eutrophic
- Trend
- ↑ Improving
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Pinellas-Seminole Lake →
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Pinellas-Seminole Lake is a productive, nutrient-rich eutrophic lake in Pinellas County, Florida. Water quality is graded D based on 1 sampling years through 2025. Overall water quality is improving over recent sampling years. Compared to the 33 other monitored lakes in Pinellas County, Pinellas-Seminole Lake ranks #25 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-04-14. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyBacteria A
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Based on E. coli testing, Pinellas-Seminole Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 17 samples across 7 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Florida’s current beach and health-department advisories before swimming.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 1.5 ft of visibility. Phosphorus level: 63 µg/L. Trophic State Index: 68.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | Not graded |
| Phosphorus | 63 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 68 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Pinellas-Seminole Lake
Compare lakeside cabins, hotels, and vacation rentals near Pinellas-Seminole Lake in Pinellas County, Florida — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Pinellas-Seminole Lake are listed below.
Top-rated places to stay near Pinellas-Seminole Lake
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Planning a whole trip? See where to stay at Florida’s top lakes →
Water Temperature
Pinellas-Seminole Lake typically sits around 85°F at the surface in September. Summer average is about 84°F. Usually warmest in Sep (about 85°F) and coldest in Jan (about 66°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 84 field readings (2010–2024) via the EPA Water Quality Portal. See the full Pinellas-Seminole Lake water temperature breakdown →
Fishing Pinellas-Seminole Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.196 m/yr | 5 |
| Phosphorus | ↑ Improving | -14.05 µg/L/yr | 5 |
EPA Impairment Status
Pinellas-Seminole Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4B).
Causes of impairment
Source: EPA ATTAINS assessment unit FL1618 · Official waterbody report · Matched by proximity (1.33 km)
County Ranking
Ranked #25 of 34 lakes in Pinellas County
Nearby Lakes With Higher Grades
Pinellas-Seminole Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Pinellas County
Frequently asked questions about Pinellas-Seminole Lake
Where is Pinellas-Seminole Lake?
- Pinellas-Seminole Lake is a lake in Pinellas County, Florida. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Pinellas-Seminole Lake?
- Pinellas-Seminole Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 1.5 ft visibility. Phosphorus: 63 µg/L.
Is Pinellas-Seminole Lake safe to swim in?
- Based on E. coli testing, Pinellas-Seminole Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 17 samples across 7 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Pinellas-Seminole Lake has a water quality grade of D (Nutrient-rich). Bacteria levels can spike quickly after heavy rain, so always check Florida's current beach and health-department advisories before you swim.
What is the water temperature of Pinellas-Seminole Lake?
- Pinellas-Seminole Lake typically sits around 85°F at the surface in September, from 84 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Explore Pinellas-Seminole Lake across LakeQuality
More Florida Lake Rankings
Other Grade D Lakes in Florida
Eutrophic Lakes in Florida
Where this data comes from
242 measurements from 3 monitoring stations, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- FLORIDA LAKEWATCH
21FLKWAT_WQX242 samples · 2021–2025
Monitoring station identifiers (3)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database