Temperatures have climbed to 28C today as a warm flow of weather arrived from Spain and Portugal.
Sunseekers have flocked to Leeds parks and riverside spots, but West Yorkshire Police have urged people to stay out of open water.
Leeds East Neighbourhood Policing Team (NPT) said it had received calls concerned for people's safety at RSPB St Aidans, near Kippax, and other outdoor spaces.
Youths have also been spotted jumping into the River Aire near Leeds Dock.
In a statement issued on Facebook, the NPT said: "Can we take this opportunity to warn people about swimming in local nature reserves/outdoor lakes etc.
"Its that time of the year again where youths gathering outdoors to enjoy themselves, and whilst we encourage that we want them to be as safe as possible.
"We are already getting calls about St Aidans and other local outdoor spaces."
It comes as the mum of a much-loved 25-year-old Leeds teacher who died after drowning in the River Aire backs a new campaign calling on people to stay out of the water.
Lewis Howlett, 25, worked as a teacher at Farnley Academy before his tragic death in May 2020.
Lewis got into difficulty swimming in the water off Redcote Lane, Kirkstall on a Saturday night.
His friends called the emergency services but he sadly lost his life and his body was found the following morning.
His mum Joanne Howlett, 57, has called for more education in schools regarding water safety and said if Lewis had seen a similar campaign, his death could have been prevented.