Lake Seminole
Lake Seminole in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 1.6 ft visibility. Phosphorus: 60 µg/L. Surface area: 320 acres.
- Clarity
- 1.6 ft
- Typical in August
- 88°F
- Max depth
- ~38 ft est.
- Area
- 320 acres
- 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 Lake Seminole →
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Lake Seminole is a 320-acre productive, nutrient-rich eutrophic lake in Pinellas County, Florida with an estimated average depth of about 38 feet. 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, Lake Seminole ranks #17 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-03-04. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyBacteria B
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, Lake Seminole rarely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 2.7% of 111 samples across 8 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 1.6 ft of visibility. Phosphorus level: 60 µg/L. Trophic State Index: 67.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 60 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 67 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Seminole
Compare lakeside cabins, hotels, and vacation rentals near Lake Seminole 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 Lake Seminole are listed below.
Top-rated places to stay near Lake Seminole
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Florida’s top lakes →
Water Temperature
Lake Seminole typically sits around 88°F at the surface in August. Summer average is about 88°F. Usually warmest in Jul (about 88°F) and coldest in Jan (about 62°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 507 field readings (2010–2025) via the EPA Water Quality Portal. See the full Lake Seminole water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~38 ft est. |
| Average Depth | ~10 ft est. |
| Surface Area | 320 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Florida has not published bathymetry for Lake Seminole.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Lake Seminole
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.045 m/yr | 5 |
| Phosphorus | ↑ Improving | -7.5 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Lake Seminole is a man-made reservoir impounded by the Lake Seminole Dam (completed 1949), built primarily for recreation on the Long Bayou; earth-type dam, 15 ft tall and 2,000 ft long.
- Surface area
- 320 ac
- Normal storage
- 3,000 ac-ft
- Max storage
- 4,800 ac-ft
- Drainage area
- 0 sq mi
- Hazard class
- Low
- Owner
- PINELLAS COUNTY
All listed purposes: Recreation;Other.
Source: USACE National Inventory of Dams, NID ID FL00429 · Operator website
EPA Impairment Status
Lake Seminole 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
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Seminole under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger.
- Fdot District 7Tampa · 3 mi away · NPDES FLS648434Major
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #17 of 34 lakes in Pinellas County
Nearby Lakes With Higher Grades
Lake Seminole holds Grade D. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Pinellas County
Frequently asked questions about Lake Seminole
Where is Lake Seminole?
- Lake Seminole 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 Lake Seminole?
- Lake Seminole in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 1.6 ft visibility. Phosphorus: 60 µg/L. Surface area: 320 acres.
Is Lake Seminole safe to swim in?
- Based on E. coli testing, Lake Seminole rarely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 2.7% of 111 samples across 8 seasons. That works out to a bacteria swim-safety grade of B — a historical summary of past testing, not a current reading. Lake Seminole 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 Lake Seminole?
- Lake Seminole typically sits around 88°F at the surface in August, from 507 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Lake Seminole?
- No published bathymetric survey covers Lake Seminole, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 38 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 320 acres.
Explore Lake Seminole across LakeQuality
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Where this data comes from
154 measurements from 77 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples154 samples · 2020–2025
Monitoring station identifiers (77)
- 21FLPDEM_WQX-SA-B-20-05
- 21FLPDEM_WQX-SA-A-20-06
- 21FLPDEM_WQX-SA-A-20-04
- 21FLPDEM_WQX-SA-A-20-03
- 21FLPDEM_WQX-SA-A-20-08
- 21FLPDEM_WQX-SA-B-20-06
- 21FLPDEM_WQX-SA-B-20-01
- 21FLPDEM_WQX-SA-B-20-04
- 21FLPDEM_WQX-SA-A-20-05
- 21FLPDEM_WQX-SA-B-20-02
- 21FLPDEM_WQX-SA-B-20-03
- 21FLPDEM_WQX-SA-B-20-07
- 21FLPDEM_WQX-SA-A-20-01
- 21FLPDEM_WQX-SA-B-20-08
- 21FLPDEM_WQX-SA-A-20-07
- 21FLPDEM_WQX-SA-A-20-02
- 21FLPDEM_WQX-SA-A-21-06
- 21FLPDEM_WQX-SA-A-21-08
- 21FLPDEM_WQX-SA-A-21-04
- 21FLPDEM_WQX-SA-B-21-01
- 21FLPDEM_WQX-SA-A-21-03
- 21FLPDEM_WQX-SA-A-21-07
- 21FLPDEM_WQX-SA-B-21-06
- 21FLPDEM_WQX-SA-B-21-02
- 21FLPDEM_WQX-SA-A-21-05
- +52 more
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)