Winter swimming’s popularity on the rise – Real-time sea water temperature can be checked online

UiRaS beach sensors provide real-time water temperature data

UiRaS beach sensors have been measuring water temperature at around twenty locations in the Helsinki metropolitan area for five years. The beach sensors, developed and maintained by the City of Helsinki’s innovation company Forum Virium Helsinki, provide information about the water temperature online with half-hour accuracy throughout the year. The service is used by swimmers, as well as kayakers, winter swimmers, and sea rescue professionals, among others.

Several places to take a dip around Helsinki

There are over a dozen winter swimming spots in Helsinki, operated by winter swimming clubs and companies that rent out swimming locations. Some swimming spots are only available to members of winter swimming clubs, but others have open hours for all city residents. For example, operators of sauna containers can integrate the water temperature of the swimming spot on their websites thanks to open data.

Winter swimmers follow water temperatures year-round

Swimmers who regularly visit the Uunisaari winter swimming club follow the UiRaS website with interest throughout the year. “Many swimmers go for a dip in the winter regardless of the water temperature, as long as there is an ice hole and they can get into the water. In the spring, it’s nice to follow the temperature rise as the ice melts,” says Kaisa Vilhula, a Helsinki resident who visits Uunisaari.

Challenges in installing sensors in some locations

Despite the efforts, it has not been possible to permanently install UiRaS at some swimming locations. Usually, the reason is the lack of a suitable mounting location or difficult conditions, which are often found on beaches exposed to the open sea. “Well-established installation locations are floating docks and, in some cases, fixed swimming stairs. For example, there have been several UiRaS in different locations in Eiranranta, but usually, the spring ice has broken them,” says Aapo Rista, a specialist at Forum Virium Helsinki.

UiRaS: An experiment in IoT-based water temperature measurement

UiRaS is an experiment by the City of Helsinki’s innovation company Forum Virium Helsinki and the City of Helsinki’s Culture and Leisure Department, which aims to test how affordable IoT sensors perform in measuring swimming water temperature not only during the summer but also in the winter. The measurement data is published on the website as well as open data for anyone interested to use.

Photo: Mika Ruusunen, City of Helsinki