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Lake waters remarkably warm after record temps

The recent heatwave has also led to an abundance of oxygen-depleting blue-green algae in some places.

Aikuisia ja lapsia uimassa auringonlaskun aikaan.
Lake waters are significantly warmer than the seasonal mean. Image: Ismo Pekkarinen / AOP

The surface waters of lakes across Finland are significantly warmer than usual for this time of year.

The surface water temperature of Pääjärvi lake in the municipality of Karstula in Central Finland was 26 degrees Celsius on Sunday, which is more than five degrees warmer than the seasonal mean.

Elsewhere, in the southern city of Tampere, the surface waters of Näsijärvi, one of Finland's biggest lakes, was 25 degrees Celsius. The current air temperature in Tampere is 21 degrees.

Recent surveys have also found abundant levels of cyanobacteria, also known as blue-green algae, in Pääjärvi, as well as in the nearby Kyyjärvi lake.

The Finnish Environment Institute (Syke) reported an increase in the number of sightings of cyanobacteria last week. A link to the last weekly report that features a map designating the areas containing algae can be found here.

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