The INMO has described hospital overcrowding as "obscene" with trolley figures showing 679 patients waiting for a bed, the second highest recorded and the worst so far this year.
The Irish Nurses and Midwives Organisation said the hospitals worst affected are University Hospital Limerick with 63 patients on trolleys, University Hospital Cork with 60; Letterkenny University Hospital with 47 and South Tipperary General Hospital with 40.
The INMO said South Tipperary General Hospital is in crisis, because despite being one of the country's smallest hospitals, it has more patients on trolleys that some of the larger hospitals.
INMO General Secretary Phil Ní Sheaghdha described the overcrowding as obscene.
"Winter has not even started, and Irish hospitals are overwhelmed", she said.
She said staff are faced with an inhumane working environment, while patients are put at ever-increasing risk.
The highest figure ever recorded by the INMO trolley watch was 714 on 12 March 2018.
The highest for 2019 before today was 631.
The HSE's TrolleyGar figures put the number of patients waiting for a hospital bed at 526 today, with 278 waiting more than nine hours.
In a statement, the HSE said: "The HSE regrets that any patient should have to wait for admission from ED to a hospital ward. However, it is important to note that once a decision is made to admit a patient, they still remain under the care of the staff in ED until they can safely transfer to the appropriate hospital ward for their on-going care.
"While the majority of patients who attend Emergency Departments receive treatment and are discharged home, 20-30% of patients need to be admitted to hospital for further treatment and care.
"Most of our 29 Emergency Departments are reporting both high numbers of patient attendances and patients requiring admission to hospital."
The statement added: "Acute hospitals are continuing to see a year on year increase in the number of patients requiring treatment and care.
"By the end of September over 1 million patients had attended our 29 Emergency Departments, 3% more than the same time last year. Almost 263,000 were patients admitted to hospital for further treatment and care."
Minister for Health Simon Harris is due to speak to each hospital Group Chief Executive today and will also meet HSE Chief Executive Paul Reid.
The minister said that the Department of Health secured €26 million for winter funding this year to alleviate the burden on emergency departments.
A spokesperson for the minister said he will be asking each hospital group CEO, to outline how the situation has escalated to such a level and how they intend to use the funding made available to make improvements for patients.
Speaking in the Dáil, the Taoiseach Leo Varadkar said the number of patients on trolleys was down to 317 nationally this afternoon and that he anticipated that most of the remaining patients will have beds by later tonight.
He was responding to the Sinn Féin leader, Mary Lou McDonald who said, "What we have witnessed on your watch is a complete and utter failure in health policy. For eight years now you have failed to make any inroads in tackling the trolley crisis. Three Fine Gael ministers including yourself and things haven't got any better."
Labour's health spokesperson Alan Kelly said the trolley figure trends are worrying and if they are this bad "on a fairly innocuous Tuesday, where there is no sign of bad weather or the worst of any winter viruses have yet to appear, what are the trolley numbers going to be like in the depths of winter?"
He called on the Minister Harris to publish the winter initiative plan and said "serious action matched with funding" is now needed from the minister.