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Coastal Water Temperature Guide

The NCEI Coastal Water Temperature Guide (CWTG) provides recent ocean and Great Lakes temperatures collected from buoys, tide gauges, and other monitoring stations in the United States and its territories, as well as average water temperatures. In addition to water temperature, users have access to station pages that collect data on water levels, wave heights, wind speed, and air temperature and pressure. The CWTG also includes a daily climatology layer of sea surface temperatures to allow users to see water temperatures in between physical stations. 

Interactive Map

The Coastal Water Temperature Guide includes:

To compare an area’s recent ocean temperature to its average temperature, select a station on the map or view the table of monthly averages.

Launch Interactive Map

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Data Sources

* Use the near real-time water temperature data with discretion, because they may contain errors.
* When viewing the OISST layer, note that this is a daily climatology and not real-time water temperatures.
* Short-term monthly averages are calculated from the most recent available month. For example, the average water temperature for August is calculated from the most recent August data only.

Frequently Asked Questions

What is the best water temperature for swimming in the ocean?

There's no real optimal temperature,but many people feel “comfortable” swimming in water that is 70° to 78° Fahrenheit.  

Can water temperatures differ between nearshore and offshore sites at the same latitude? 

Yes, nearshore water temperatures are more susceptible to the influence of river runoff, higher cooling and heating rates, continental air masses, near-shore ocean currents, and upwelling effects. 

Why is the water at the beach sometimes cold on warm summer days?

It could be due to a phenomenon known as upwelling, which occurs when displaced surface waters are replaced (upwelled) by colder, deeper waters. This can be caused by a persistent offshore wind blowing the warmer surface waters away from the shore.

Is it dangerous to swim in cold water?

Hot and cold water are relative, however, even in the summer, prolonged immersion in water temperatures below 70° Fahrenheit can produce hypothermia. Hypothermia, a subnormal body temperature, can occur in waters with cold or even moderate temperatures. The body quickly surrenders its heat to cold water, and chilled blood can impair the heart and brain. Swimming or treading water will greatly increase heat loss and may limit your range to less than one-half mile. Use H.E.L.P. (Heat Escape Lessening Posture) if alone, or huddle with others. This can possibly extend your survival time. 

More on cold water survival

There are no buoys or tide stations near my beach. How can I see what the water temperature is closer to me?

You can use the satellite climatology layer to get an approximate temperature for beaches and other coastal areas that aren’t near a buoy or tide station. This layer doesn’t provide real time temperature, but it's a close approximation that can be used for recreational purposes.