Fingal County Council has issued a 'Prior Warning Notice' for Velvet Strand, Portmarnock and Loughshinny Beach which remains valid for a six-day period.
The council says a water sample is due to take place on Thursday, and results will be available on Saturday.
They are advising that for now people avoid swallowing water, avoid swimming with an open wound, and also do not swim if you are pregnant or have a weakened immune system.
They are also advising people to wash their hands before handling food if they are at either beach.
The council said "Beach users are asked to respect the advisory notice as it has been put in place to ensure that the health of bathers is not compromised."
FCC has issued a Prior Warning Notice for Velvet Strand, Portmarnock and Loughshinny Beach
Bathers are advised of the possibility of an increase in the levels of bacteria in the bathing water due to the forecast of heavy rainfall
More info below or at https://t.co/ttYfUFnUMm pic.twitter.com/wPCC7rvtFK— Fingal County Council (@Fingalcoco) August 24, 2020
