Hospitals faced a surged in demand on their A&E departments last month as a summer heatwave causes increases in health conditions linked to hot weather.
NHS trusts around the country saw unprecedented demand as almost 2.2m people turned up at A&E for treatment - a record figure.
Increases in people suffering breathing problems and more elderly people needing treatment for dehydration were among the causes.
It meant hospitals continued to struggle with their targets for 95 per cent of A&E patients to be admitted, transferred or discharged within four hours.
At Leeds Teaching Hospitals 83.9 per cent of A&E patients were seen in four hours last month.
Deputy Chief Executive Suzanne Hinchliffe said: “We have seen an increase in the number of people attending A&E compared to last year.
“There was a particularly noticeable increase of very sick patients attending in July, which means they need to stay longer in hospital and this has an impact on how quickly we can see people in A&E.”
A&E performance has improved at the Leeds trust after just 68.9 per cent of patients were seen in four hours at the start of the year.
Prof Hinchliffe, said: “The number of people we see within four hours has improved considerably since winter.
“This can largely be linked to fewer patients in beds across our hospitals, with more patients being discharged sooner.”
NHS England said accident and emergency departments helped 100,000 more people in July compared with the same period last year - a five per cent increase. Emergency admissions were up six per cent.