Lake Mid
Lake Mid in St. Johns County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 2.1 ft visibility. Phosphorus: 103.5 µg/L.
- Clarity
- 2.1 ft
- Typical in August
- 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 Lake Mid →
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Lake Mid is a productive, nutrient-rich eutrophic lake in St. Johns County, Florida. Water quality is graded D based on 1 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 6 other monitored lakes in St. Johns County, Lake Mid ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2024-11-14. 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 2.1 ft of visibility. Phosphorus level: 103.5 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.1 ft | Not graded |
| Phosphorus | 103.5 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Mid
Compare lakeside cabins, hotels, and vacation rentals near Lake Mid in St. Johns 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 Mid are listed below.
Top-rated places to stay near Lake Mid
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 Mid typically sits around 85°F at the surface in August. Summer average is about 84°F. Usually warmest in Jul (about 86°F) and coldest in Jan (about 55°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 22 field readings (2017–2024) via the EPA Water Quality Portal. See the full Lake Mid water temperature breakdown →
Fishing Lake Mid
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.35 m/yr | 2 |
| Phosphorus | ↑ Improving | -7.08 µg/L/yr | 5 |
EPA Impairment Status
Lake Mid is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit FL2320C · Official waterbody report · Matched by proximity (1.06 km)
County Ranking
Ranked #3 of 7 lakes in St. Johns County
Nearby Lakes With Higher Grades
Lake Mid 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 St. Johns County
Frequently asked questions about Lake Mid
Where is Lake Mid?
- Lake Mid is a lake in St. Johns 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 Mid?
- Lake Mid in St. Johns County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 2.1 ft visibility. Phosphorus: 103.5 µg/L.
Is Lake Mid safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Lake Mid has a water quality grade of D (Nutrient-rich). Always check local health department advisories before swimming.
What is the water temperature of Lake Mid?
- Lake Mid typically sits around 85°F at the surface in August, from 22 EPA Water Quality Portal field readings (2017–2024). That is a typical value for the month, not a live reading.
Explore Lake Mid across LakeQuality
Planning a trip around Castillo de San Marcos?
Lake Mid is about 13 miles from Castillo de San Marcos National Monument. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Castillo de San Marcos →More Florida Lake Rankings
Other Grade D Lakes in Florida
Eutrophic Lakes in Florida
Where this data comes from
58 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples58 samples · 2020–2024
Monitoring station identifiers (1)
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