Fountainstown, Garryvoe, Tragumna, Youghal's Front Strand and Claycastle beaches have all been issued with Prior Warning notices by Cork County Council.
"Bathers are advised of the possibility of an increase in the levels of bacteria in the bathing water over the coming days due to the possible localised heavy rainfall."
Beaches in Ireland often see elevated bacteria levels in the days following heavy rain as water from nearby hills and farms runs enters the sea.
The Council warned bathers to reduce the risk of illness by taking the following precautions; avoid swallowing or splashing water; wash your hands before handling food; avoid swimming with an open cut or wound; and avoid swimming if you are pregnant or have a weakened immune system.
The warning for the five beaches will remain in place until Wednesday.
The public can stay updated on the water quality at the website www.beaches.ie