Questions and answers
Everything people ask about our numbers, where they come from, and what they mean.
Photo: Lionelmayne, CC BY-SA 3.0, via Wikimedia Commons
Using the site
How often is the data updated?
The whole site rebuilds every hour. Wind and weather forecasts refresh each time. Water levels and temperatures refresh as often as the agency that measures them publishes, which ranges from every 15 minutes to once a day. Every number on a lake page shows how old it is, so you never have to guess.
Why does one lake show a water temperature and another doesn't?
Because someone has to measure it. Only a fraction of the world's lakes have a sensor in the water or a scientific model covering them. Where we have a reliable source, we show it and name it. Where we don't, we say so rather than estimating a number that would look authoritative and be wrong.
Can I switch between °F and °C?
Yes. The buttons at the top of every page switch temperatures, wind speeds, water levels, and distances together, and your choice is remembered on your device.
How do I find lakes near me?
Use the “Lakes near me” button on the homepage or the all-lakes page. Your browser will ask permission first, and your location is only used inside your browser to sort the list. It is never sent to us or stored.
My lake isn't listed. Can you add it?
Often, yes. We add a lake when we can show something real for it, which usually means an official gauge or a reliable temperature source. Send us the lake's name and country, and a link to an official data source if you know of one, and we will look into it.
Water levels
What does “percent full” actually mean?
It compares the usable water a reservoir is holding against the amount it holds when full, not the depth of the lake. A reservoir at 50% full is not half as deep as usual; it is holding half its usable supply. Some sources publish this figure and some do not, which is why you will see it on Texas reservoirs but not on every lake.
Why is a lake “below normal” but not close to empty?
These answer different questions. “Below full” compares today with the level a reservoir reaches when completely full, which many lakes rarely are. “Below normal for this date” compares today with the median level for the same calendar date across every year on record, which is usually the more meaningful comparison. A lake can sit well below full and still be entirely normal for September.
How do you work out what is normal?
For lakes with a long record, we take the median level for the same date across every year available, using a three-day window either side so each date has enough readings. We only make the comparison when at least five separate years are available, and we show the full range for that date as well as the median. Some of our lakes have more than 80 years of records.
Why do two websites show different levels for the same lake?
Usually because they are showing different things. A lake's height above sea level and a gauge's own reading are different numbers, and agencies also use different sea-level reference systems that can differ by a foot or more. On top of that, some sources publish a daily average while others publish the latest instant reading. We always label which number we are showing and where it came from.
Is the water level exact?
It is as exact as the agency's own published figure, but nearly all live water data is provisional, meaning it has been published automatically and not yet reviewed. Readings can be corrected later. It is good enough for planning a trip, not for legal or engineering purposes.
Swimming and safety
What water temperature is comfortable for swimming?
Most people find 70 °F (21 °C) and above pleasant, and 77 °F (25 °C) and above properly warm. Below 70 °F counts as cold water and deserves respect, and below 60 °F is where cold water shock becomes a serious risk for anyone not used to it. Our guide on how cold is too cold explains why.
Is the temperature you show the same everywhere in the lake?
No, and this matters. We show a surface temperature measured or modelled at one point. A shallow sunny bay can be several degrees warmer than open water a few hundred metres away, and there is often a sharp cold layer a metre or two down. Treat our reading as a good guide, not a promise.
Can I rely on Lakedip to decide whether it is safe to go in?
No. We give general information to help you plan, not a safety assessment. Conditions change fast, local hazards do not appear in any dataset, and official warnings, signs, and lifeguards always come first. If you hear thunder, get off the water regardless of what any website says.
What do the “good for today” verdicts mean?
They are rules of thumb calculated from the current wind, gusts, and water temperature: enough wind to sail, too much to paddle comfortably, warm enough to swim, and so on. The thresholds we use are published on our How our data works page. They describe conditions, not your ability or your equipment.
Where the data comes from
Who measures all this?
Public agencies and research institutes, and we name them on every page. Wind and weather forecasts come from Open-Meteo, which combines national weather services. US water levels come from the US Geological Survey and state agencies such as the Texas Water Development Board. Great Lakes levels and temperatures come from NOAA. Alpine lake temperatures come from Eawag, the Swiss Federal Institute of Aquatic Science and Technology.
Is Lakedip connected to any of those agencies?
No. We are an independent site and not endorsed by any of them. We name them because they do the hard work of measuring lakes and deserve the credit, and because you should be able to check any number we show.
What is the difference between a measurement and a lake model?
A measurement comes from a sensor in the water. A lake model is a scientific simulation that calculates temperature from the weather, the lake's shape, and past measurements. Models from research institutes are usually within a degree or two of reality, but they are still estimates. Every page says which one you are looking at.
I think a number is wrong. What should I do?
Tell us, and include the lake's name, what looked wrong, and roughly when you saw it. We check every report. Sometimes it is a broken sensor at the source, which we can then hide until it is fixed.
About Lakedip
Does Lakedip cost anything?
No. The site is free and has no accounts.
Do you show ads?
No. The site carries no ads and no paid links. If that ever changes, we will say so clearly next to any link that earns us money, and it will never change the conditions we show.
Do you use cookies or track me?
No cookies, no tracking, no accounts. The only thing stored on your device is whether you prefer °F or °C, and that never leaves your browser.
Why are the photos of real lakes?
Because a stock photo of a generic sunrise tells you nothing about the lake you are looking up. Our photos come from Wikimedia Commons under licences that allow commercial use with credit, and the photographer and licence are named on every page that shows their work.
Something else?
Look up a term in the glossary, read how our data works, or get in touch.