Water temperature at a beach can be measured in several ways, and they don’t always agree.
In-water sensors
- NOAA tide stations on piers and harbors report every 6 minutes. They’re often the closest measurement to where people swim.
- NOAA and partner buoys (National Data Buoy Center) report hourly. Some sit right off the beach; others are many miles offshore, where water can be colder or warmer than at the shore.
- USGS gauges measure temperature in some bays, estuaries, lakes and reservoirs.
Satellite estimates
The NASA/JPL MUR analysis combines several satellites into a daily, roughly 1 km map of sea surface temperature. It covers the whole coast and large lakes, but it’s a “foundation” temperature: the temperature just below the surface before daytime warming. On a sunny afternoon, shallow water at the beach can be noticeably warmer. The analysis is also usually a day or two behind.
How we pick the number you see
- A recent reading from an in-water sensor close to the location, if one exists.
- Otherwise, the latest satellite estimate for the nearest water.
- Offshore buoys appear as extra context, never as the headline beach temperature.
Every page names the source, its distance and the time of the reading. See the water temperature methodology.
Sources: NOAA NDBC; NOAA Tides & Currents; NASA JPL MUR SST.