The charity is anticipating that the weekend, from Friday, August 23 to Monday, August 26, will be one of the busiest of the year.
High spring tides are expected, which will increase water movement and the likelihood of tidal cut-offs.
Forecasted conditions include sunshine, strong winds, and medium to large surf.
Guy Botterill, regional lifeguard lead for the South West, said: “We are expecting some warm weather and fairly rough conditions this bank holiday weekend.
“We hope everyone has an enjoyable and safe weekend on the coast.”
The RNLI advises anyone heading to the coast to go to a lifeguarded beach, and if swimming or bodyboarding, to do so only between the red and yellow flags.
If anyone does get into trouble, the RNLI reminds them to “float to live.”
The best way to float is to tilt the head back with ears submerged, relax and breathe normally.
Movement of hands can help maintain floatation.
Once breathing is under control, help can be called or a safe swim initiated.
Mr Botterill added: “It is imperative that if you are heading to the coast you follow the RNLI’s advice and head to a lifeguarded beach where our teams will be performing patrols from 10am to 6pm each day.
“Swimming or bodyboarding should only be done between the red and yellow flags, as it is the safest place to do so.”
RNLI has been saving lives at sea for 200 years, with the special anniversary on March 4.
The charity, reliant on public donations, will be running events throughout the year to honour its history and inspire future lifesavers.
More information can be found on the official RNLI website: rnli.org/.
To find the nearest lifeguarded beach, visit rnli.org/find-my-nearest/lifeguarded-beaches.