Myrtle Lake
Myrtle Lake in Seminole County, Florida has a water quality grade of C (Fair). Water clarity: 2.8 ft visibility. Phosphorus: 45 µg/L.
- Clarity
- 2.8 ft
- Typical in August
- 87°F
- Type
- Eutrophic
- Trend
- → Stable
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Myrtle Lake is a productive, nutrient-rich eutrophic lake in Seminole County, Florida. Water quality is graded C based on 1 sampling years through 2025. Water clarity is improving over recent sampling years. Compared to the 121 other monitored lakes in Seminole County, Myrtle Lake ranks #97 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-07-01. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyModerate
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Very murky, less than 2.8 ft of visibility. Phosphorus level: 45 µg/L. Trophic State Index: 61.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.8 ft | Not graded |
| Phosphorus | 45 µg/L | Fair |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 61 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Myrtle Lake
Compare lakeside cabins, hotels, and vacation rentals near Myrtle Lake in Seminole 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.
Top-rated places to stay near Myrtle Lake
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Planning a whole trip? See where to stay at Florida’s top lakes →
Water Temperature
Myrtle Lake typically sits around 87°F at the surface in August. Summer average is about 87°F. Usually warmest in Jul (about 87°F) and coldest in Jan (about 63°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 84 field readings (2010–2025) via the EPA Water Quality Portal. See the full Myrtle Lake water temperature breakdown →
Fishing Myrtle Lake
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.094 m/yr | 6 |
| Phosphorus | ↓ Declining | +4 µg/L/yr | 5 |
EPA Impairment Status
Myrtle 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 FL2986D · Official waterbody report · Matched by proximity (1.32 km)
County Ranking
Ranked #97 of 122 lakes in Seminole County
Nearby Lakes With Higher Grades
Myrtle Lake holds Grade C. 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 Seminole County
Frequently asked questions about Myrtle Lake
Where is Myrtle Lake?
- Myrtle Lake is a lake in Seminole County, Florida. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Myrtle Lake?
- Myrtle Lake in Seminole County, Florida has a water quality grade of C (Fair). Water clarity: 2.8 ft visibility. Phosphorus: 45 µg/L.
Is Myrtle Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Myrtle Lake has a water quality grade of C (Fair). Always check local health department advisories before swimming.
What is the water temperature of Myrtle Lake?
- Myrtle Lake typically sits around 87°F at the surface in August, from 84 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
Explore Myrtle Lake across LakeQuality
More Florida Lake Rankings
Other Grade C Lakes in Florida
Eutrophic Lakes in Florida
Where this data comes from
82 measurements from 2 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 samples82 samples · 2020–2025
Monitoring station identifiers (2)
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