Thomas Lake
Portage County, Wisconsin32 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Thomas Lake. Here is what has been measured.
- Curly-Leaf Pondweed
- 28 ft max depth
- Public access
- Limited data
Thomas Lake in Portage County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 13 ft visibility. Maximum depth: 28 ft. Surface area: 32 acres.
Wisconsin DNR lists Panfish as common on Thomas Lake. DNR survey details →
Thomas Lake is a 32-acre lake in Portage County, Wisconsin with a maximum depth of 28 feet. Overall water quality is declining over recent sampling years. The lake supports 4 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-18. Methodology: how these readings are compared.
What Thomas Lake is good for
From access and monitoring records, not editorial picks.
- Clear water13 ft of visibility
- Boat launch1 documented ramp
- Fishing4 species recorded
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Thomas Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Thomas Lake
These are the measurements Wisconsin DNR publishes for Thomas Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 13 ft. TSI 40.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 13ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| 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. | 40 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Thomas Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Thomas Lake typically sits around 69°F at the surface in September. Summer average is about 77°F. Usually warmest in Jul (about 80°F) and coldest in Apr (about 49°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (49°F) to its warmest (80°F).
Typical surface water temperature by month, from 21 field readings (2025–2026) via the EPA Water Quality Portal. See the full Thomas Lake water temperature breakdown →
Wisconsin DNR lists Panfish as common on Thomas Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thomas Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 2013. 1 station on file (most recent sample 2026).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Thomas Lake covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2025Thomas Lake spring shocking, 2025Spring Shocking Survey · WI DNR · 2025 (PDF)
Lake Details
Max depth
28 ft
Surface area
32 acres
Public access
Yes
Listed by Wisconsin DNR
Recreation & Access
- Thomas LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Thomas Lake
Compare lakeside cabins, hotels, and vacation rentals near Thomas Lake in Portage County, Wisconsin — 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 Thomas Lake
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Follow Thomas Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Thomas Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water quality readings over time
2 seasons of samples on record (2025–2026). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Nearby Lakes in Portage County
Frequently asked questions about Thomas Lake
Where is Thomas Lake?
- Thomas Lake is a lake in Portage County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Thomas Lake?
- Thomas Lake in Portage County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 13 ft visibility. Maximum depth: 28 ft. Surface area: 32 acres.
Is Thomas Lake 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 Thomas Lake?
- Thomas Lake typically sits around 69°F at the surface in September, from 21 EPA Water Quality Portal field readings (2025–2026). That is a typical value for the month, not a live reading.
How deep is Thomas Lake?
- Thomas Lake has a maximum depth of 28 feet. The lake covers 32 acres.
What fish are in Thomas Lake?
- Fish species found in Thomas Lake include Panfish, Largemouth Bass, Northern Pike, Trout. Thomas Lake is located in Portage County, Wisconsin.
What did the DNR fisheries survey find at Thomas Lake?
- Wisconsin DNR lists Panfish as common on Thomas Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thomas Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Thomas Lake?
- Thomas Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Thomas Lake. Public access is listed as yes.
Can I fish at Thomas Lake?
- Thomas Lake 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 Wisconsin's fish and wildlife agency, so check its current regulations before you go.
Explore Thomas Lake across LakeQuality
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Where this data comes from
7 measurements from 1 monitoring station, 2025–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX7 samples · 2025–2026
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
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory