Coastal floodwater covering a patio: white chairs and a picnic table stand in moving brown water up to their seats, with a submerged dock, a half-buried fence, and the far shoreline behind them.

Know when coastal water is rising.

Get the iPhone app Text and email alerts
Tidal flooding on a Chesapeake Bay shoreline. Photograph by CoastWarn.

Flood alerts on your iPhone today. Text and email are not live yet.

Free to download, with NWS coastal flood warnings and live water levels included.

Alert channels

What each channel gives you

All three watch the same NOAA water-level readings. They differ in where the message lands and how much you can tune it.

Text message

A short message to your mobile number when water at your gauge crosses a National Weather Service flood stage, and one when it drops back. Reply STOP any time to cancel.

Not live yet No app needed

Email

The same alerts as a message you can keep, forward, or filter. Each one names the gauge, the reading, and the flood stage it crossed, and carries an unsubscribe link.

Not live yet No app needed

CoastWarn for iPhone

Adds a live water-level chart, the station map, and your own alert threshold instead of the default flood stages. Free to download, with NWS coastal flood warnings and live levels included.

$19.99 one-time lifetime unlock for CoastWarn's own threshold alerts. No subscription.

Sign up

Get flood alerts by text or email

Give us a ZIP code and we match it to the nearest NOAA tide gauge. We name that gauge and its distance before anything is switched on, and you confirm the message we send before a single alert follows.

How it works

How text and email signup will work

  1. Your place

    You give a ZIP code. We find the closest NOAA CO-OPS tide gauge to it and tell you its name and how many miles away it is.

  2. Your channel

    You pick text, email, or both, and tick consent for each one separately. Picking email does not ask for your phone number.

  3. Your confirmation

    We send one message to each channel you chose. Nothing else is sent until you answer it. Each channel is confirmed on its own.

Sources and limits

Where the readings come from, and what they cannot tell you

  • Water levels come from NOAA CO-OPS tide gauges — the same public observations NOAA publishes.
  • Flood stages are the National Weather Service minor, moderate, and major levels published for each gauge, not thresholds we invented.
  • Coastal flood watches and warnings come from the National Weather Service product for the gauge's zone.
  • A gauge is not your address. A reading describes water at that gauge. How it reaches any particular street depends on elevation, wind, drainage, and ground that no tide gauge measures.
  • Readings are periodic, not continuous. Water can cross a flood stage between checks, and a gauge can go offline.

Not affiliated with NOAA or the NWS; a supplement, not a replacement, for official warnings.

Follow your local emergency management and official National Weather Service warnings. CoastWarn does not promise that a message will arrive, or arrive in time to act on.

Questions, or want your details removed? Write to support@memoryforge.app. Our Privacy Policy and Terms of Service say what we keep and for how long.

Get CoastWarn for iPhone

The iPhone app has the live chart, the station map, and your own threshold. Text and email alerts need nothing installed, and are not live yet.

Get the iPhone app Text and email alerts