Support
Email support@cleartoswim.com and a person will answer. Tell us your iPhone model, your iOS version, and what the app showed when the problem happened. If it is a wrong verdict, the time and your rough location help us trace it.
Reporting a wrong verdict
This is the report we care about most. If the app said open when a storm was on top of you, or stayed closed long after the sky cleared, send it in. Include the time, the radius and wait time you had set, and a screenshot if you have one.
Common questions
Where do I get it?
On the App Store. ClearToSwim went live on 24 September 2026 and is free to download.
Free. iPhone, iOS 15.1 or later.
What does it run on?
iPhone. There is no Android version and no web version. That is what we built first.
Where does the lightning data come from?
From NOAA's GOES weather satellites, which carry the Geostationary Lightning Mapper and watch for lightning from orbit across the Americas. Our server reads that public data and your app asks our server, so your phone is never talking to a lightning network directly. Two things follow from the source being a satellite: it sees flashes inside clouds as well as those that reach the ground, which is useful early warning, and it fixes each flash to roughly the right place rather than the exact one. Coverage and detection rates vary, which is why no app can promise it sees every strike. NOAA does not endorse ClearToSwim.
Where in the world does it work?
Where the GOES satellites look, which is the Americas and the Pacific: North, Central and South America, the Caribbean, Hawaii and the wider Pacific, out to about 52 degrees north and south. Most of Alaska sits past that northern edge, and so do Europe, Africa, the Middle East, Asia and Australia. Those are two geostationary satellites rather than a worldwide network, so the boundary is fixed rather than something that fills in later. You can still add a pool anywhere. If it falls outside that view the app says so on the pool itself, because a pool with no lightning data reaching it would otherwise look exactly like a calm afternoon.
What comes with the free app, and what is Pro?
The free app is the red and green stoplight, and it stays free: red when lightning is detected inside your radius, green once the all-clear wait has run, and an alert for each. ClearToSwim Pro lights the amber lamp in between, which is two further states: a caution stage while lightning is near but still outside your evacuation radius and the pool is open, and a countdown stage while a closed pool is nearly ready to reopen. The free app shows the first of those as open and the second as closed, so the light never turns green early. Pro also unlocks the radius and wait settings, which is the next answer.
Can I change the radius and the wait time?
With ClearToSwim Pro, yes. The defaults are 10 miles and 30 minutes, which follow National Weather Service guidance and common aquatic-facility practice, and the free app runs those defaults. Pro lets you set the radius from 1 to 35 miles in 1-mile steps and the wait from 10 to 60 minutes in 5-minute steps. If your facility has its own written policy, match it.
Why did the countdown restart?
Because a new strike landed inside your radius. That is the 30-minute rule working as intended: the clock runs from the last strike, not the first one. It is also the part that is easiest to get wrong when counting by hand.
Does it work without a data connection?
No. Lightning data arrives over the network. With no signal the app cannot update, and it will tell you that rather than show a stale verdict as if it were current.
Does it need my location?
It needs a pool location to watch. You can grant location access once to put the pin where you are, or place it yourself. See the privacy policy for what happens to that location.
Is this a replacement for a lifeguard or an official warning?
No. It is one more thing to look at, not a replacement for either. If you see lightning or hear thunder, get out of the water and go inside, whatever the app says.
ClearToSwim is an informational aid, not a safety guarantee. Always follow official warnings. If you see lightning or hear thunder, get out of the water and take shelter in a substantial building or a hard-topped vehicle. Wait until 30 minutes after the last thunder before returning to the water.