Swimmers had to leave Huddersfield Leisure Centre in trunks and bikinis and then wait in the chilly car park during a fire evacuation drill.
Customers were handed flip-flops and foil blankets as they walked, dripping and shivering, from the pool to the car park at 11am on Tuesday.
An Examiner reader took photos from a discreet distance as people waited to be let back in.
A spokeswoman for Kirklees Active Leisure, which runs the facility, said health and safety regulations dictated that four evacuation tests be carried out during the year.
She said the evacuation drills had to be staggered throughout the year to ensure all staff were fully up to speed at all times.
The customers were outside for “five minutes max,” she added.
“We do provide people with flip flops and foil blankets to keep them warm.”
Once everyone is out, staff sweep the building to ensure nobody is left inside.
Posters had been placed around the leisure centre in recent weeks which warned customers that an evacuation drill would be taking place.
“We have apologised for any inconvenience but we can’t say which date it is going to happen. We do try to do it when it’s not raining or snowing. Ultimately, it is for the safety of customers.”