One person was on board the vessel at the time, and volunteer crews carried out a welfare check before giving advice to the skipper.
The yacht was later able to refloat on the incoming tide.
A spokesperson for Penarth RNLI said: “Our D class was tasked to a yacht aground at the entrance to Cardiff Bay this morning.
“With one person aboard and strong onshore winds we were asked to assess the casualty and ensure no further assistance was required.
“Our crew carried out a welfare check and gave advice to the skipper, the vessel was later able to refloat successfully on the incoming tide.
It also happened to be crewmember Jen Williams’ birthday.
This was the second ‘birthday’ shout for Penarth RNLI this month, joking that they’re “getting used to sourcing cake for the crew on recovery”.
