The NHS is likely to see the "winter crisis" extend into the summer, according to new analysis by doctors.
Hospitals can expect their summer performance in A&E departments to be as poor as in recent winters, the British Medical Association (BMA), which represents doctors, warned.
The health service came under unprecedented pressure this winter, with A&E attendances, waiting times and admissions reaching alarming levels in England.
The figures - based on data from NHS England - suggest the worst-case scenario for July, August and September could see 6.2 million attendances at A&E over the period, along with 774,000 people waiting for more than four hours to be seen.
This would equate to just 87.5% of patients being seen, admitted or discharged within four hours, with 147,000 trolley waits of four or more hours and 1.57 million emergency admissions.
It said the best-case scenario would be comparable to the winter of 2015, with 5.89 million attendances at A&E over the summer and 89.6% meeting the target of being seen, admitted or discharged within four hours.
That would mean 613,000 people having to wait longer than that, it said.
The best-case scenario would involve 1.51 million emergency admissions and 127,000 trolley waits of four hours or more.
The BMA said that traditionally, the summer offers a period of respite for the NHS, and while attendances at A&E tend to increase, bed occupancy falls as emergency admissions go down.
With more beds available, it means trusts can improve performance against the four-hour wait target and reduce trolley waits.
It said the implications for trusts are that winter contingency plans continue to remain in place, giving the example of University Hospitals of North Midlands NHS Trust, which is planning to keep its extra winter capacity open until the summer.
BMA council chairman Dr Chaand Nagpaul said: "This data clearly shows what doctors working on the front line have been saying for some time that the winter crisis has truly been replaced by a year-round crisis.
"Doctors and patients have just endured one of the worst winters on record, resulting in thousands of cancelled operations, unacceptable long waits to be seen and people who are already at their most vulnerable having to face the indignity of being treated in hospital corridors.
"We cannot accept that this is the new normal for the NHS."
While the summer months would normally see the situation ease, the BMA believes levels of demand and activity this summer will mirror winters of two or three years ago.
Using official data from the last five years, the BMAs health policy team forecast a number of scenarios for this summers NHS performance, measured in A&E attendances, waiting times, admissions and trolley waits.
The worst-case scenario would see the health service experience a repeat of scenes experienced during winter 2016.
The BMA estimates that health funding in England is more than £7 billion a year behind comparable European countries and this could rise to over £11 billion over the next three years.
NHS England previously said this winter has seen NHS staff having to work in a "perfect storm" of appalling weather, persistently high hospital admissions due to flu and a renewed spike in norovirus."
An NHS England spokesperson said: "The NHS has faced continued pressure after one of the coldest winters in 30 years."
A Department of Health and Social Care spokesperson said: "We know that demand continues to grow, and that staff have never worked harder, which is why we gave a pay rise to more than 1.2 million dedicated staff, and why we supported the NHS with an extra £2.8 billion, on top of a planned £10 billion a year increase in its budget by 2020/21.
"The Prime Minister and Health and Social Care Secretary have committed to a fully funded, long-term plan for the NHS, which will be agreed with NHS leaders, clinicians, and health experts."