Readings from thousands of buoys and stations in 33 countries, updated all day long. Zoom in on a coast, a lake or a river, then tap a point.
This map shows the temperature of the water in seas, lakes and rivers, recorded by thousands of buoys, tide gauges and stations. It covers 33 countries, from the west coast of North America to the shores of Europe, Asia and Oceania. It is open to everyone, with no account. It updates all day long.
Every marker says where its value comes from. The shape tells what kind of information it is, the colour tells the temperature: blue for cold water, up to orange for warm water.
Tap or click a point to open its card: station, source, time of the measurement, the range between the available products and, at sea, the gap from the day's normal.
Below 15 °C the water is cold: the cold takes your breath away and tires you quickly, even when you swim well. Below 10 °C it is very cold and time in the water must stay short. The map shows a warning in both cases. Between 20 and 25 °C most people find the water pleasant. A lake or a river warms up and cools down faster than the sea: check the time of the measurement.
The sea lags behind the air. It takes weeks to warm up and as many to cool down. In the Northern Hemisphere it is warmest in late August and September, well after the hottest days; in the Southern Hemisphere, in February and March. A lake follows the season more closely and peaks in July or August, in January or February in the south. A mountain river stays cold all summer, fed by melting snow. A small lowland river can pass 25 °C at the end of a summer afternoon, then lose five degrees overnight.
For a given month, see the monthly normals, country by country. For today, the warmest water in the world.
Cold water always comes as a shock. For the first few seconds your breathing races: that is cold shock, normal and short-lived. Get in slowly, face last, then let your breath settle before you swim. Stay close to the shore the first few times. Get out before you feel cold: the shivering comes after you leave the water, not while you are in it. Have warm clothes and a hot drink waiting on the bank. Never swim alone in cold water. Below 10 °C, a few minutes are plenty.
Measurements come from public agencies and open programmes: NOAA, the USGS, Environment and Climate Change Canada, and national hydrological and weather services. Estimates come from satellites (NOAA, NASA) and models. A measurement older than 48 hours is no longer shown.
There is no official threshold. Most people are comfortable from 20 °C. Between 15 and 20 °C it is brisk but doable once you are used to it. Below 15 °C it is a cold-water swim, and a short one. Winter swimmers go into water at 5 °C, after months of practice.
A buoy offshore, a wharf in a sheltered harbour, a river mouth: three different waters a few kilometres apart. The depth of the sensor matters too, since the surface warms faster than the metre below it. Take the point closest to your spot and the most recent reading.
A satellite measures the ocean surface over a cell several kilometres wide, averaged over the day. Offshore it is accurate to within about a degree. Near the coast, in a shallow bay or off a river mouth, the gap can be larger. That is why an estimate is always drawn differently from a measurement.
Stations send their readings every few minutes or every hour, depending on the network. The map reads them again throughout the day. Each point shows how old its reading is; after 48 hours it disappears.
The usual sea temperature at that spot on that date, worked out from years of satellite records. The difference shown tells you whether the water is warmer or colder than usual.
Country by country · Sources and credits · Create my account
Cookies, yes or no?
The site works without them. If you accept, Google Analytics counts visits to help us improve it. Learn more