A health board has revised its emergency admissions policy after an 82-year-old cancer patient waited nearly four hours in the back of an ambulance.
Kathleen Clarke, from Criccieth, Gwynedd, arrived outside Ysbyty Gwynedd, Bangor at 1815 GMT on Tuesday.
Her family claimed 12 ambulances were waiting at one stage but the health board said it was no more than eight.
It apologised and blamed "severe pressures" in the bad weather.
According to her family Mrs Clarke was left waiting in an ambulance outside the hospital until 2200 GMT before being admitted to the accident and emergency department.
As a result, Betsi Cadwaladr University Health Board said it had revised its emergency admission policy in order to differentiate between medical and emergency department cases so that patients are processed more quickly.
Mrs Clarke's daughter, Carole Owen, said the situation "distressing" for her mother.
"It's just not acceptable for someone, especially an elderly person, to have to wait in an ambulance for four hours.
"They're already bewildered and this just adds to their confusion.
"It was very distressing for her."
A spokesman said the busy period lasted from the middle of the afternoon until around 2200 GMT.
In a statement the health board said: "We would like to apologise to Mrs Clarke and her family.
"The emergency department at Ysbyty Gwynedd experienced severe pressures yesterday due to the continuing adverse weather conditions.
"Whilst we make every effort to ensure that patients do not have to wait in ambulances outside hospitals for long periods."
It was a matter of always ensuring that patients can be bought safely into the hospital and "that we have the capacity to care for them appropriately".