As many as 25,000 people flocked to Barry Island on Friday as temperatures hit 30°C in some parts of Wales.
People lined the beach and nearby promenade looking to make the most of the sunny weather.
One visitor to the seaside town said there was "not too much social distancing going on but people are not going wild".
Transport for Wales warned people to allow extra time for their journey if they are travelling back from Barry on Friday evening.
The rail operator said on Twitter that they "are aware of the significant increase of passengers heading down to Barry Island to enjoy the sunshine" but "have crowd management in place".
British Transport Police are working with rail staff to help try and make sure people are abiding by the lockdown rules and wearing face coverings on public transport.
Face coverings became mandatory on public transport in Wales on Monday 27 July.
Police were patrolling the seafront and advising people to keep their distance in the long queues for food and drink at the cafes alongside the amusement arcades.
Vale of Glamorgan Council Officers and members of Safer Vale Partnership were also out, enforcing rules against alcohol.
Current lockdown rules mean that people who do not live together have to remain two metres apart. People can form an extended household with one other household, so long as the people in that group remain the same.
From Monday 3 August, gatherings of up to 30 people are allowed to take place outside if everyone above the age of 11 is social distancing.