The areas are not safe for swimming because of changing water levels and uneven ground.
The ESB has warned of the dangers of swimming in the waters at the reservoirs of Poulaphouca, and Golden Falls.
It said these areas are not appropriate for swimming because of the risk of deep and fast-flowing waters, changing water levels and uneven ground.
Ahead of the hot weather this weekend and with the improving spell of warm weather over the summer months, ESB is reminding the general public of the dangers and potentially serious consequences of swimming in any ESB reservoir.
These waters include the reservoirs at Poulaphouca in County Wicklow, Golden Falls and Leixlip in County Kildare.
Temperatures are set to reach 24 degrees with strong sunshine in parts this weekend.
Met Eireann forecaster Andrew Doran Sherlock has advised people to put on sun cream.