Police patrols have been stepped up at Stowe Pool in Lichfield after a man in his 50s died after getting into difficulty in the water.
It came only days after the death of a man at Chasewater Reservoir, while a teenager also died at a quarry near Stourport.
Carl Storer, aged 21, died while trying to rescue a nine-year-old girl at Chasewater.
An 18-year-old boy then died after entering the water at Shavers End Quarry near Stourport.
The third incident in a matter of days happened when Michael Hirsch died at Stowe Pool.
Council bosses have grappled with the challenge of how to stop people going for a swim in hot weather.
Staffordshire County Council says it believes warning signs at Chasewater are sufficient.
The county's fire service has now issued an alert for people not to go into lakes and other open bodies of water. The fire service has put up posters around Stowe Pool in an effort to hit home the message.
Lichfield station Manager Rob Horton, who attended the incident, said: “It is extremely sad to see another fatal incident in the water in Staffordshire and our thoughts are with the man’s loved ones at this difficult time.
“Although some of these spaces are beautiful places to visit, please do not under any circumstances enter the water. Only swim in designated and supervised areas.
“We know it can be tempting to go into the water to cool off during the hot weather, but there are hidden hazards under the surface. Even if the water seems calm, the underlying current can be deceiving.
“The temperature can also be colder than you expect even when the weather is warm. You can still go into cold water shock, leaving you unable to swim to the edge.
“The service has put posters around Stowe Pool to discourage swimming and will be looking into more ways to spread the message that the water is not safe to swim in. Please think before you swim.”
Ross Macleod, community safety manager at the RNLI, said: "Cold water shock is a very real and present risk for people trying to cool off in open water at the moment, and relevant both around the coast and for inland lakes, reservoirs and rivers.
"Cold water shock is a reaction that, when entering cold water suddenly, can cause someone to uncontrollably gasp and breathe in water, this is particularly dangerous at the moment because water temperatures are still very cold at around 12C (53F), despite air temperatures being much warmer."