Dozens of swimming sites under health warnings as warm weather strains water quality

Health risks at open-water swimming sites in the Netherlands have doubled since the start of the season, with warnings, advisories, and closures now affecting dozens of locations, according to an ANP analysis based on Zwemwater.nl data. Authorities report that 67 of roughly 950 official outdoor swimming locations—including lakes, ponds, and other recreational waters—currently carry either a warning or a negative swimming advisory. Four additional sites are under investigation, and swimming is fully prohibited at three locations.

A swimming ban has been in place at Almeerderstrand in Almere since June 2. Tests there did not show elevated levels of blue-green algae, enterococci, or E. coli bacteria, but the province has kept the restriction in place as a precaution. Officials say more research is needed to determine whether the water is safe for public use. Two additional swimming bans remain active at locations in Gelderland, both at holiday parks, where restrictions have been in place for a longer period. Despite these limitations, 872 official swimming sites remain open and are considered safe for recreational use across the country.

Weather conditions are adding pressure to already strained water quality. On Saturday, temperatures are expected to rise to about 16 to 19 degrees Celsius nationwide, with locally up to around 20 degrees in the southeast.

The Netherlands is seeing a mix of cloud cover, sunshine, and scattered showers, with the northwest more exposed to passing rain and the south largely staying dry.

Forecasters say the weekend weather pattern remains unsettled, with showers continuing in some regions before a gradual warming trend develops later, increasing the risk of algae growth and bacterial spread in open water.