Lake Water Temperatures
Typical surface water temperature for 3,434 lakes across 10 states, month by month — from real EPA field readings. See which lakes are warmest, when they peak, and whether the water is warm enough to swim.
Warmest lakes right now (typical for September)
| Lake | State | Typical in September | Summer peak |
|---|---|---|---|
| Lake Mariam | Florida | 92°F | 87°F |
| Pasadena Lake Westside | Florida | 90°F | 87°F |
| Crooked Lake @ Center of N Lobe | Florida | 90°F | 86°F |
| Hillsborough-Hog Island Lake | Florida | 89°F | 84°F |
| Lake Frances | Florida | 88°F | 89°F |
| Como Lake | Florida | 88°F | 85°F |
| Roper Lake | Florida | 88°F | 87°F |
| Gem Mary Lake | Florida | 88°F | 87°F |
| Lake Kennedy | Florida | 87°F | 87°F |
| Saratoga Lake West Outlet | Florida | 87°F | 87°F |
| Polesout Lake | Florida | 87°F | 87°F |
| Kbarse Lake | Florida | 87°F | 88°F |
| Seminole-Howell Lake | Florida | 87°F | 87°F |
| Greenwood Lake | Florida | 87°F | 89°F |
| Lake of the Woods | Florida | 87°F | 87°F |
Water temperatures by state
Most-monitored lakes
The lakes with the deepest temperature records — the ones people most often ask about.
More lake data
Frequently asked questions
How do you know a lake's water temperature?
We compute a typical (climatological) temperature for each month from real surface-water field readings collected by state and federal agencies and published through the EPA Water Quality Portal. It tells you what is typical for a given month at that lake — not the temperature at this exact moment.
Why not show the live water temperature?
Very few lakes have a real-time temperature gauge — only a small number of large lakes carry USGS sensors. A monthly climatology is the honest, comparable answer for every lake: it is based on actual readings and covers thousands of lakes that have no live sensor. Where a lake does have a live gauge, we show that reading on its report card.
What water temperature is comfortable for swimming?
Most people find 70–80°F comfortable for swimming without a wetsuit. Below 70°F feels brisk; below 60°F is cold enough to warrant a wetsuit; and below 50°F carries a real cold-water-shock risk. Warm water (80°F+) is very comfortable but can also favor blue-green algae in nutrient-rich lakes, so check for advisories.
More on lake temperature and swimming
Typical lake surface temperatures month by month and state by state, from years of monitoring readings — when lakes warm up, how warm they get, and when they turn.
The month when well-graded lakes in each state are typically warmest, from long-run Water Quality Portal readings rather than this year’s weather.
The highest-graded lakes for swimming, ranked on EPA nutrient and algae data — plus the one thing a letter grade cannot tell you the day you go.
How to tell a harmless algae bloom from toxic blue-green algae, what cyanobacteria look like up close, the risk to people and dogs, and where to check.
About this data
Water temperatures are a climatology — the typical value for each month, averaged from real surface-water field readings collected by state and federal agencies and published through the EPA Water Quality Portal. They describe what to expect, not the temperature right now.