Emergency services saw a surge in reports of people swimming in potentially dangerous open water during the heatwave.
The news comes after more than a dozen people are feared to have drowned in seas, rivers, lakes, canals, and quarries across England during the last 10 days.
Warm weather is expected to continue into this weekend and officers are urging the public not to be tempted to swim in unsafe open waters.
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Swimmers have been spotted at locations including the River Nene at Wadenhoe, Corby Boating Lake, Kinewell Lake at Denford, Summer Leys Nature Reserve at Wollaston and Naseby Reservoir.
However, Northamptonshire’s police and firefighters warn that ALL open water poses potential hidden dangers.
Detective Superintendent Joe Banfield said: “The tragic news of people losing their lives after swimming in rivers, lakes and canals has highlighted once again the potential dangers of such activities.
“Sadly, over the last few days, we have also seen an increase in calls to our control room reporting both adults and children swimming at locations across the county including country parks, reservoirs and lakes.
“With the high temperatures set to continue into the weekend and schools closing for the summer, we would urge people not to be tempted to cool down in any open water where authorised swimming is not permitted.
“Not only is the water temperature a lot colder than the air but all open water can contain other hidden hazards which may not be visible from the surface including unpredictable depths of the water, weeds, reeds and other unknown objects.”
According to Mail Online, a man in his 20s has become the latest to drown after attempting to cool off from the scorching temperatures by going for a swim at a water park in Wiltshire.
Swimming in undesignated sites at country parks breaches park bylaws and managers also say it can be disturbing for local wildlife inhabiting the waterways.
Organised open water swimming sessions at both Daventry and Sywell Country Parks is currently suspended.
Blue-green algae bloom identified at both sites is toxic to both people and pets.