Hospitals in England are so overcrowded ahead of Christmas care is being put at risk, experts say, with some places having to turn away ambulances because they cannot accept any more patients.
NHS England's first weekly report of the winter shows nearly 95% of beds are occupied. Anything above 85% is unsafe.
Experts warned hospitals were in the "red zone" and it was a risk to care.
The data for last week showed eight A&Es had diverted ambulance crews elsewhere because they were so busy.
And even when ambulances were able to drop patients off, significant numbers were facing delays.
Ambulance crews are meant to be able to handover patients to A&E staff within 15 minutes of arrival - but in one in nine cases it took over 30 minutes.
An NHS England official said staff were "working hard" to keep up with demand.
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"As the colder weather begins to set in, it's vital that the NHS and local authorities continue to work together to help people stay well and out of hospital wherever possible.
"The public can also help NHS staff by making sure they have their free flu jab if eligible and by using NHS 111 as their first port of call for non-emergencies."
It is more than a year since any part of the UK has hit one of its three key targets - for:
- A&E waits
- cancer care
- hospital operations
The extra money announced by the government in the summer will not start reaching the front line until next year.
Siva Anandaciva, of the King's Fund think tank, said the figures showed the NHS was "already under tremendous strain".
"Despite a mild start to winter and low flu levels, targets are still being badly missed.
"These figures show little slack in a system, which is operating consistently in the red zone.
"Hospital bed occupancy levels are already higher than recommended levels, the point at which hospitals are so full that good patient care is put at risk."
Shadow health secretary Jonathan Ashworth said: "Winter is only just beginning for our NHS and these are hugely concerning figures that don't bode well for the difficult weeks ahead."