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Marine Warnings Glossary

If you’re on or near large bodies of water, you should know what the following marine weather warnings mean, and what actions to take to remain safe.

But first, a marine primer:

What’s the difference between “miles per hour” and “knots per hour”?

  • 1 knot = 1 nautical mile per hour = 6,076 feet per hour
  • 1 mph =1 mile per hour = 5,280 feet per hour

So a car going about 35 miles per hour would travel at the same speed as a boat going about 30 knots. Wind blowing at around 75 miles per hour on land would blow at around 65 knots over water.


Small Craft Advisory – This alert is issued when there are current or future weather or sea conditions that might be hazardous to small boats. If you see a Small Craft Advisory pennant displayed, immediately tune your radio to the latest marine forecast. The threshold conditions for this advisory are usually 18 knots of wind (less in more dangerous waters) or hazardous waves.

Gale Warning – This indicates wind speed has reached 34 to 47 knots in your area.

Storm Warning
– This is issued when winds reach speeds above 47 knots. However, if the winds are the result of a tropical storm or hurricane, this warning means winds are forecasted between 48 and 63 knots.

Hurricane Watch – When a hurricane threatens an area, a Hurricane Watch is issued that instructs people living within that area to listen to their radio or television for further advisories, and to take precautionary action in case Hurricane Warnings are issued.

Hurricane Warning – If winds of 64 knots or above are forecast because of a hurricane, a Hurricane Warning is issued for your area. Take immediate defensive action.

Special Marine Warning
– If a severe local storm is not covered by the preceding warnings or advisories, a Special Marine Warning is broadcast. No visual displays are used with this warning. Boaters should tune into a National Oceanic & Atmospheric Administration (NOAA) Weather radio station or to Coast Guard or commercial radio stations that transmit marine weather information.


See our Weather Glossary

See our Hurricane Glossary

See our Marine Warnings Glossary

See our Astronomical Terms and Definitions Glossary

See our Gardening Terms Glossary

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