New analysis by doctors has shown the NHS "winter crisis" is likely to extend into the summer.
The British Medical Association (BMA) has warned hospitals can expect their summer performance in A&E departments to be as poor as in recent winters.
The health service came under unprecedented pressure this winter, with A&E attendances, waiting times and admissions reaching alarming levels in England.
In the summer this would normally ease, however the BMA thinks levels of demand and activity this summer will mirror winters of two or three years ago.
Analysis used official NHS England data from the last five years to create a forecast for 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 figures 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.
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."