Lake South
St. Johns County, FloridaView mapDirections
Florida DEP publishes the water-quality measurements for Lake South. Here is what has been measured.
- Eutrophic
- Public access
Lake South in St. Johns County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 78 µg/L.
Lake South is a productive, nutrient-rich eutrophic lake in St. Johns County, Florida. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 6 other monitored lakes in St. Johns County, Lake South ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2024-12-02. Methodology: how these readings are compared.
What Lake South is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
Readings onlyElevated nutrients
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.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Lake South 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.
Water quality measurements for Lake South
These are the measurements Florida DEP publishes for Lake South, 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 1.6 ft of visibility. Phosphorus 78 µg/L. TSI 68.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 78µg/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. | 68 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lake South
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lake South typically sits around 79°F at the surface in October. Summer average is about 84°F. Usually warmest in Jul (about 87°F) and coldest in Jan (about 54°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (54°F) to its warmest (87°F).
Typical surface water temperature by month, from 20 field readings (2017–2024) via the EPA Water Quality Portal. See the full Lake South water temperature breakdown →
Recreation & Access
- Guana River Recreation Area - River Access RampPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Lake South
Compare lakeside cabins, hotels, and vacation rentals near Lake South 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Lake South are listed below.
Top-rated places to stay near Lake South
Prices for Oct 16–18, 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 trip? Cabins and lodging at Lake South → · more Florida lake trips
Follow Lake South’s readings
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Fishing Lake South
Water Quality Trend: Worsening
Based on 5 years of monitoring (2020–2024).
Phosphorus
Worsening+17.97 µg/L/yr5 years
Nearby Lakes in St. Johns County
Frequently asked questions about Lake South
Where is Lake South?
- Lake South is a lake in St. Johns 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 South?
- Lake South in St. Johns County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 78 µg/L.
Is Lake South safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Lake South?
- Lake South typically sits around 79°F at the surface in October, from 20 EPA Water Quality Portal field readings (2017–2024). That is a typical value for the month, not a live reading.
Are there boat ramps on Lake South?
- Lake South has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Guana River Recreation Area - River Access Ramp. Public access is listed as yes.
Can I fish at Lake South?
- Lake South has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Florida's fish and wildlife agency, so check its current regulations before you go.
Explore Lake South across LakeQuality
Planning a trip around Castillo de San Marcos?
Lake South is about 9 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 lakes in Florida
Other Lakes in Florida
Eutrophic Lakes in Florida
Where this data comes from
70 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 samples70 samples · 2020–2024
Monitoring station identifiers (1)
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.
Other records on this page
Named boat-access points from the USGS National Boat Ramps inventory