Flood watch vs. flood warning

Checked against FEMA and other official sources · Last reviewed October 8, 2026

The five flood alerts, from least to most serious

The National Weather Service (NWS) labels each alert with what you should do: be aware, be prepared, or take action.

• Flood Advisory (be aware). Issued "when flooding is not expected to be bad enough to issue a warning." NWS adds that it "may cause significant inconvenience, and if caution is not exercised, it could lead to situations that may threaten life and/or property."
• Flood Watch (be prepared). Issued "when conditions are favorable for flooding. It does not mean flooding will occur, but it is possible."
• Flood Warning (take action). Issued "when flooding is imminent or occurring."
• Flash Flood Warning (take action). Issued "when a flash flood is imminent or occurring." NWS says: "If you are in a flood prone area move immediately to high ground."
• Flash Flood Emergency. The most severe level of a flash flood warning, used for "an extremely dangerous weather hazard capable of catastrophic damage and a severe threat to human life." NWS says this kind of warning includes the phrase "FLASH FLOOD or TORNADO EMERGENCY," so for floods it reads as a flash flood emergency.

The short version: a watch means get ready; a warning means act now. [1][3]

What is a flash flood?

NWS defines a flash flood as "a sudden violent flood that can take from minutes to hours to develop." It adds: "It is even possible to experience a flash flood in areas not immediately receiving rain."

NWS issues Flash Flood Warnings when "a rapid, damaging, and life-threatening rise of water into a normally dry area is happening or imminent." Other floods can build more slowly. NWS notes that sometimes forecasters can anticipate where a flood will happen days or weeks ahead, while flash floods "can occur within minutes and sometimes without any sign of rain." [1][4][5]

Flash flood warnings: base, considerable and catastrophic

Flash flood warnings use an impact-based format with "damage threat" tags: - No tag (base). Used most of the time, when flash flood damage is possible. - Considerable. NWS uses it "rarely," when flash flooding of unusual severity is imminent or ongoing and urgent action is needed to protect lives and property. - Catastrophic. Used "exceedingly rarely," when a flash flood threat to life and catastrophic damage is occurring or imminent, and floodwaters "have risen or will rise to levels rarely if ever seen." This is the level that NWS calls a flash flood emergency.

The tag also decides whether your phone buzzes. NWS sends Wireless Emergency Alerts only for flash flood warnings tagged "Considerable" or "Catastrophic." A base-level flash flood warning is still a warning to act, even if your phone stays quiet. [3][4][6]

What to do under a watch

A watch is your time to get ready. NWS's before-a-flood advice includes: - Know whether your home, work or school is in a floodplain, where water collects on roads you travel, and the fastest way to higher ground. - Keep enough food, water and medicine for at least 3 days, plus batteries, flashlights, a first aid kit and a NOAA Weather Radio or other battery-operated radio. - Charge your phone and portable radios. - Pack in advance in case you are evacuated. - If it is likely your home will flood, NWS says don't wait to be ordered to leave: evacuate yourself.

A watch is usually too late to buy flood insurance for that storm. NWS notes that insurance companies stop issuing policies if there is a threat of flooding and that many flood insurance policies take at least 30 days to go into effect. Ready.gov puts it as typically up to 30 days, and says homeowner's insurance policies do not cover flooding. See do I need flood insurance? and what flood zone am I in? [5][7]

What to do under a warning

Ready.gov's advice if you are under a flood warning: - Find safe shelter right away. - Do not walk, swim or drive through flood waters. - Stay off bridges over fast-moving water. - Evacuate if told to do so, or move to higher ground or a higher floor, depending on the type of flooding.

NWS adds: - If you live in a flood-prone area or are camping in a low-lying area, get to higher ground immediately. - If told to evacuate, do so immediately. - Don't go into a basement, or any room, if water covers the electrical outlets or if cords are submerged. - If you are trapped by moving water, move to the highest possible point and call 911 if possible.

If you are trapped in a building, Ready.gov says to get to the highest level, and not to climb into a closed attic, where rising water could trap you. Go on the roof only if necessary, and signal for help. If your car is trapped in rapidly moving water, stay inside it; get on the roof if water is rising inside the car. [2][7]

Turn Around, Don't Drown

NWS says that "each year, more deaths occur due to flooding than from any other thunderstorm related hazard." Citing CDC, it reports that "over half of all flood-related drownings occur when a vehicle is driven into hazardous flood water." The next highest share of flood deaths comes from walking into or near flood waters.

It takes less water than most people think. On its Turn Around Don't Drown page, NWS says: - "A mere 6 inches of fast-moving flood water can knock over an adult." - "It takes just 12 inches of rushing water to carry away most cars and just 2 feet of rushing water can carry away SUVs and trucks."

NWS's flood-safety page puts the vehicle figures slightly differently: "12 inches of water can float a car or small SUV, 18 inches of water can carry away large vehicles." Either way, about a foot of moving water can take a car.

Never drive around barriers blocking a flooded road. NWS warns that the road may have collapsed under the water, and that water "may be deeper than it appears and can hide hazards" such as sharp objects, washed-out road surfaces and electrical wires. "It is NEVER safe to drive or walk into flood waters." [2][8]

How to get flood alerts

Wireless Emergency Alerts (WEA). These look like text messages, with a special tone and vibration repeated twice. NWS says no signup is required: alerts are sent automatically to WEA-capable phones, and they are free. Remember that NWS sends WEA for flash flood warnings only when the damage threat is considerable or catastrophic, so don't rely on your phone alone.

NOAA Weather Radio All Hazards. A nationwide network of radio stations that broadcasts official NWS warnings, watches, forecasts and other hazard information 24 hours a day, 7 days a week. You need a special radio receiver or scanner that can pick up the signal.

Local alerts. Ready.gov recommends signing up for your community's warning system. The Emergency Alert System (EAS) and NOAA Weather Radio also provide emergency alerts. [6][7][9]

Questions people ask