Where is Lake Seminole?

Lake Seminole is a lake in Pinellas County, Florida. Its water-quality measurements are published by Florida DEP and shown on this page as reported.

Is Lake Seminole safe to swim in?

Based on E. coli testing, Lake Seminole occasionally exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 9.1% of 55 samples across 8 seasons. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Lake Seminole is safe to swim in today is a call for Florida's water agency and the county health department; check their current beach advisories before you swim.

What is the water temperature of Lake Seminole?

Lake Seminole typically sits around 81°F at the surface in October, from 186 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.

Lake Seminole

Pinellas County, Florida320 acresView map Directions

Florida DEP publishes the water-quality measurements for Lake Seminole. Here is what has been measured.

Clarity

1 ft

Murkier than most

Secchi · sampled 2025

Phosphorus

75 µg/L

More phosphorus than most

Measured by Florida DEP

Water temp

~81°F

Typical for Oct · EPA WQP

Area

320 acres

Surface area

Type

Hypereutrophic

Trophic class

Trend

Improving

5 years of samples

Hypereutrophic
Impaired · Algal growth

See the measurements Directions Where to stay

Lake Seminole in Pinellas County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 1 ft visibility. Phosphorus: 75 µg/L. Surface area: 320 acres.

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Lake Seminole is a 320-acre highly nutrient-loaded hypereutrophic lake in Pinellas County, Florida. Overall water quality is improving over recent sampling years. Compared to the 33 other monitored lakes in Pinellas County, Lake Seminole ranks #21 for water quality.

Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-03-04. Methodology: how these readings are compared.

Lake Seminole covers about 320 acres in Pinellas County. For a place on the water, look through cabin and lake-house rentals near Lake Seminole on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.

Swimming conditions

Readings only

Recreation use not supported

Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.

Bacteria testing record

from E. coli testing · 55 samples, 8 seasons

Based on E. coli testing, Lake Seminole occasionally exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 9.1% of 55 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.

Whether Lake Seminole is safe to swim in today is a call for the Florida Department of Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

Get alerts for Lake Seminole →

Water quality measurements for Lake Seminole

These are the measurements Florida DEP publishes for Lake Seminole, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

Very murky, less than 1 ft of visibility. Phosphorus 75 µg/L. TSI 72.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)	1ft	Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	75µg/L	Poor GoodFairPoor
Chlorophyll-a (algae)		No reading The green pigment in algae — a direct measure of how much algae is in the water.
Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a.	72	Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic

Very high nutrients, dense algae, poor clarity

Ask about Lake Seminole

Answers come straight from the public measurements and survey records on this page.

Water Temperature

Lake Seminole typically sits around 81°F at the surface in October. Summer average is about 87°F. Usually warmest in Aug (about 88°F) and coldest in Jan (about 62°F). These are typical values by month — not a live reading.

62°

Jan

70°

Feb

71°

Mar

76°

Apr

83°

May

87°

Jun

87°

Jul

88°

Aug

85°

Sep

81°

Oct

73°

Nov

68°

Dec

Column height runs from this lake’s coldest month (62°F) to its warmest (88°F).

Typical surface water temperature by month, from 186 field readings (2010–2025) via the EPA Water Quality Portal.

Lake Details

Surface area

320 acres

No bathymetric survey has been published for Lake Seminole, so its depth is not documented here.

Stays via Stay22

Stays 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Lake Seminole are listed below.

Top-rated places to stay near Lake Seminole

Prices for Oct 9–11, 4 adults. Change dates on the map below.

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 →

Follow Lake Seminole’s readings

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Fishing Lake Seminole

→ Lake Seminole fishing regulations (limits, seasons, special rules)

Water Quality Trend: Improving

Based on 5 years of monitoring (2020–2024).

Water clarity
Improving
5 years
Phosphorus
Improving
-13.65 µg/L/yr5 years

See year-by-year chart →

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

Algal growthNutrients (phosphorus, nitrogen)pH / acidity

Designated uses not supporting: Aquatic life, Recreation.

Source: EPA ATTAINS assessment unit FL1618 · Official waterbody report

Nearby Lakes in Pinellas County

Pinellas-Seminole Lake1.5 ft clear · Eutrophic0.1 miView →Lake Seminole1 ft clear · Hypereutrophic0.6 miView →Lake Seminole1.6 ft clear · Eutrophic1.7 miView →Mckay Creek LakeMesotrophic2.5 miView →Taylor Lake—View →Pinellas-Jungle North Inlet Lake1.5 ft clear · Hypereutrophic4.3 miView →

Frequently asked questions about Lake Seminole

Where is Lake Seminole?: Lake Seminole is a lake in Pinellas County, Florida. Its water-quality measurements are published by Florida DEP and shown on this page as reported.
What is the water quality of Lake Seminole?: Lake Seminole in Pinellas County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 1 ft visibility. Phosphorus: 75 µg/L. Surface area: 320 acres.
Is Lake Seminole safe to swim in?: Based on E. coli testing, Lake Seminole occasionally exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 9.1% of 55 samples across 8 seasons. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Lake Seminole is safe to swim in today is a call for Florida's water agency and the county health department; check their current beach advisories before you swim.
What is the water temperature of Lake Seminole?: Lake Seminole typically sits around 81°F at the surface in October, from 186 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.

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Where this data comes from

151 measurements from 76 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 samples151 samples · 2020–2025

Monitoring station identifiers (76)

EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.