Woodgreen staff have been handing out cold drinks to people standing in queues across the car park at the Banbury Open Air Pool.
Swimming lessons between 4pm - 5pm have been cancelled.
On the hottest day of the year the pool has gone online to warn that it is not allowed to let more than 300 people in.
So families standing in the sweltering sun are being allowed in one by one as people leave.
Management have warned that they will not accept any abuse of staff who are having to observe the capacity rules.
The pool Facebook page said: "We try to get everybody in as quickly and safely as possible, but we only have space for 300 people in our swimming pool. This can at times mean we have to go one out, one in . Sometimes, it may not even be possible for that and we have to accept that we are at maximum capacity. This is for the safety of you all and us.
"We will NOT accept abuse to our staff in ANY circumstances. If this occurs, you will be asked to leave the facility and the police may be called.
"Please be sure to bring water, protection for your skin, hat/sunglasses etc. The queue may be very long and it is due to be warm."