Coastal Flood Advisory, Watch, or Warning: how to read the water and act

The words describe different products

Outlook, forecast, advisory, watch, and warning are not interchangeable

A planning outlook can identify days when high tide flooding is more likely. A water-level forecast estimates how high the water may reach. An NWS alert adds a defined area, time, expected impacts, and protective action. Read the entire product because local thresholds and impacts differ from one shoreline to the next.

High-tide flooding outlook

NOAA's annual and monthly outlooks show when high tide flooding may be more likely at specific locations. They support long-range planning; they are not a forecast that a particular street will flood and are not a watch or warning.

Water-level forecast

Estimates total water level at a tide-gauge location for the next hours or days. It can combine tide and weather effects, but it is not itself an evacuation order or an NWS alert.

Coastal Flood Advisory

Minor coastal flooding is expected, imminent, or occurring. Low-lying roads, parking areas, yards, and storm drains may flood. “Minor” does not make moving water or a closed road safe.

Coastal Flood Watch

Significant coastal flooding is possible, but important details such as exact timing, location, or severity remain uncertain. Prepare to protect property and leave if local officials or a later warning tell you to act.

Coastal Flood Warning

Moderate or major coastal flooding is expected, imminent, or occurring. Serious impacts to people, property, roads, and structures are possible. Take the actions in the warning and follow local evacuation directions immediately.

Translate the gauge into local impact

A tide height is useful only when you know its local reference point

NOAA tide stations report observed water, predicted astronomical tide, and sometimes a forecast water level. The same number can mean different things at different stations because elevations, tidal datums, seawalls, drainage, roads, and flood thresholds are local. Do not compare raw tide heights between cities.

NOAA's Coastal Inundation Dashboard overlays observations, tide predictions, available forecasts, and known flood-impact thresholds. It also displays active NWS Coastal Flood Advisories, Watches, and Warnings. Use the station nearest the affected area, then read the local NWS product for street-level consequences.

Why the water rises

High tide, storm surge, waves, wind, and rain can combine

Coastal inundation is the total water level over normally dry ground. NOAA identifies several contributors: unusually high tides, storm surge, persistent onshore wind, and waves. Rainfall and river runoff can add water in tidal rivers and estuaries. This is why a forecast focused on only one ingredient can miss the decision you need to make.

• High tide flooding: overflow onto typically dry coastal land during high tides; it can happen on a sunny day.
• Storm surge: an abnormal rise of water generated by a storm above the predicted astronomical tide. A separate Storm Surge Watch or Warning may be issued for tropical-cyclone danger.
• Wave action: can send water and debris beyond the still-water level and damage shore roads, dunes, seawalls, and structures.
• Onshore wind: can pile water toward the coast over several tide cycles, including during non-tropical storms.
• Rain and runoff: can worsen flooding where storm drains, rivers, and tidal waterways cannot drain efficiently.

A Coastal Flood Warning, a Storm Surge Warning, a Flash Flood Warning, and a Tsunami Warning answer different hazard questions. More than one can be active. Never assume one product cancels or replaces another.

Prepare before the next high tide

Protect the route, the essentials, and the exit—not only the building

Coastal flooding often peaks near high tide, but roads and drainage can become unusable earlier and remain flooded later. A safe plan accounts for the whole trip, including bridges, causeways, parking areas, and low approaches.

1. Know whether your home, workplace, school, and usual routes are in low-lying coastal or tidal areas.
2. Identify at least two routes to higher ground and a place to stay outside the flood-prone area.
3. Move vehicles, medicines, documents, mobility equipment, pet supplies, and irreplaceable items before access is cut off.
4. Charge phones and backup batteries. Keep more than one way to receive official alerts.
5. Clear safe, accessible drains only before flooding begins. Never enter moving water or expose yourself to electrical hazards.
6. Follow local instructions for sandbags, flood barriers, utility shutoff, evacuation zones, and road closures.

When water reaches roads or property

Do not let the tide clock become a reason to wait

The posted time of high tide is not a guarantee that flooding will begin or end at that minute. Water can arrive early, peak later, or stay trapped by wind, waves, rainfall, or poor drainage. Treat observed impacts and official instructions as the decision point.

1. Leave when authorities tell you to evacuate. Do not wait to watch the water reach a familiar landmark.
2. Never drive around a barricade or through water of unknown depth. The road may be washed out or energized.
3. Move to higher ground if water is rising around you. Call 911 if you are trapped and can do so safely.
4. Stay away from beaches, seawalls, rocks, piers, storm drains, and fast-moving tidal channels during hazardous conditions.
5. Keep children and pets away from floodwater, which can contain debris, sewage, chemicals, and hidden drop-offs.
6. Do not enter a flooded basement or room if water may contact outlets, appliances, or wiring.

After the water falls

A falling gauge does not automatically make the area safe

Floodwater can leave damaged pavement, unstable foundations, contaminated mud, displaced wildlife, live electrical hazards, and saltwater damage. Access may remain restricted after the alert expires or the tide recedes.

• Return only when public officials say the route and property are safe to enter.
• Photograph damage from a safe location before cleanup when appropriate.
• Avoid standing water near electrical equipment and report downed lines.
• Use protective clothing for cleanup and follow local drinking-water and sanitation guidance.
• Check the next tide cycle and updated forecast; repeat flooding may follow before cleanup is complete.