Waikato Hospital is also seeing an increased number of respiratory cases and was busy with trauma cases at the weekend.
The clinical director of Middlemore's emergency department, Dr Vanessa Thornton, said yesterday that the hospital had used parts of its crisis management plan to cope with the surge.
"[On Monday], 356 patients presented to the emergency department, which is the highest ever. The previous high was two years ago on Boxing Day - 330."
The total had exceeded 300 daily since Friday and had been in the 290s earlier last week. It was usually around 275, Dr Thornton said.
"The hospital is blocked."
It had postponed some outpatient clinics so it could beef-up staffing of acute services, was putting inpatients in areas such as the gastro-enterology day-stay unit and, to fill gaps caused by staff sickness, was using bureau nurses and asking doctors to work overtime or extra shifts.
"... [yesterday] morning there were 23 patients sitting in the emergency department waiting for a [ward] bed which is extremely unusual for us.
"Unfortunately we've had some patients going up to eight hours, which hasn't been happening for us in the last couple of years."
Since late last week, the emergency department had slipped below 90 per cent on the Government goal of admitting, transferring or discharging 95 per cent of patients within six hours.
Dr Thornton said many patients had respiratory infections that were exacerbating underlying chronic breathing disorders such as emphysema or asthma.
The rate of wintertime respiratory infections had increased since temperatures plunged in mid-August.
"What we are wanting people to do is see their GP early, stay on top of their chronic emphysema or asthma and have their inhalers at home."
"Part of the increase is in the 15-to-39-year-old age group. These are the people that don't often attend a GP. These are the people we want to get to see a GP earlier and have their inhalers on hand."
Other hospitals are reporting similar problems. Rotorua, Tauranga and Taupo hospitals are almost full, with Tauranga getting about 180 cases a day.
Auckland DHB's general manager of operations, Ngaire Buchanan, said yesterday Auckland City Hospital and Starship children's hospital had a late-winter peak of patients.
"We have maintained our winter plans over this period to reduce the impact of this demand for our patients at this stage."
Government figures published yesterday showed Counties Manukau DHB (Middlemore) continued to meet the six-hour emergency department target in the April-June quarter and Auckland met it for the first time.
Waitemata fell short by one percentage point, but board officials said it had consistently met the target during July.
The chairman of the Auckland and Waitemata DHBs, Lester Levy, said the reductions in time patients spent in emergency departments were a remarkable turn-around and had been maintained despite a heavy winter workload and record numbers of patients.