Thorpe Park is banning visitors from putting their hands in the air while riding its roller coasters following complaints about body odor.
The new rule will apply at the theme park in Chertsey, Surrey, from Wednesday and signs will tell visitors to keep their arms down and 'Say no to BO'.
With temperatures expected to reach 84F (29C), managers expect an excess of perspiration as visitors queue to go on rides.
Wardens on the rides will also remind people to consider their fellow passengers and anyone ignoring the warnings will be escorted off. Those who continue to do so will be asked to leave the park.
Mike Vallis, a director at Thorpe Park, said: "We've found that when the temperature tops 77F (25C) the level of unpleasant smells can become unacceptable and we do receive complaints.
"Our rides are really scary and people tend to sweat more than normal due to the fear and anticipation they experience while queuing up so it can get really pongy. Therefore, we felt a ban in temperatures of 25C plus would be the best way to ensure our guests have the most enjoyable experience and aren't exposed to any unsavory armpits."