Harbor Isles Lake
Harbor Isles Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 1.6 ft visibility. Phosphorus: 95 µg/L.
- Clarity
- 1.6 ft
- Typical in August
- 88°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 Harbor Isles Lake →
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Harbor Isles Lake is a productive, nutrient-rich eutrophic lake in Pinellas County, Florida. Water quality is graded D based on 1 sampling years through 2022. Overall water quality is improving over recent sampling years. Compared to the 33 other monitored lakes in Pinellas County, Harbor Isles Lake ranks #15 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2022-10-05. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyElevated nutrients
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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 1.6 ft of visibility. Phosphorus level: 95 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 95 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 70 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Harbor Isles Lake
Compare lakeside cabins, hotels, and vacation rentals near Harbor Isles 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 Harbor Isles Lake are listed below.
Top-rated places to stay near Harbor Isles Lake
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Planning a whole trip? See where to stay at Florida’s top lakes →
Water Temperature
Harbor Isles Lake typically sits around 88°F at the surface in August. Summer average is about 89°F. Usually warmest in Jul (about 90°F) and coldest in Jan (about 64°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 60 field readings (2020–2022) via the EPA Water Quality Portal. See the full Harbor Isles Lake water temperature breakdown →
Fishing Harbor Isles Lake
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.15 m/yr | 3 |
| Phosphorus | ↑ Improving | -8.5 µg/L/yr | 3 |
EPA Impairment Status
Harbor Isles Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit FL1661G · Official waterbody report · Matched by proximity (0.58 km)
County Ranking
Ranked #15 of 34 lakes in Pinellas County
Nearby Lakes With Higher Grades
Harbor Isles Lake 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 Harbor Isles Lake
Where is Harbor Isles Lake?
- Harbor Isles 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 Harbor Isles Lake?
- Harbor Isles Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 1.6 ft visibility. Phosphorus: 95 µg/L.
Is Harbor Isles Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Harbor Isles Lake has a water quality grade of D (Nutrient-rich). Always check local health department advisories before swimming.
What is the water temperature of Harbor Isles Lake?
- Harbor Isles Lake typically sits around 88°F at the surface in August, from 60 EPA Water Quality Portal field readings (2020–2022). That is a typical value for the month, not a live reading.
Explore Harbor Isles Lake across LakeQuality
More Florida Lake Rankings
Other Grade D Lakes in Florida
Hillsborough County · 2 ft
Hillsborough County · 3.3 ft
Hillsborough County · Nutrient-rich
Hillsborough County · Nutrient-rich
Hillsborough County · Nutrient-rich
Hillsborough County · Nutrient-rich
Eutrophic Lakes in Florida
Where this data comes from
110 measurements from 4 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples110 samples · 2020–2022
Monitoring station identifiers (4)
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