Hospital services in Wakefield, Pontefract and Dewsbury had their busiest month ever in April.
The Mid Yorkshire NHS Hospitals Trust, which runs all three sites, said the public needed to "choose wisely" over where they go to seek treatment, adding that Accident and Emergency (A&E) should only be used by people with serious and life-threatening injuries.
Last month also saw an outbreak of the norovirus at Dewsbury Hospital, which has now been dealt with, the trust said.
The factors behind the sudden spike in hospital attendances are unclear, though one senior doctor said he hoped the improving weather would help ease pressure on NHS services.
Speaking on Tuesday, the chair of the Wakefield Clinical Commissioning Group, Dr Phil Earnshaw, said: "Mid Yorkshire had their busiest seven days in Accident and Emergency (A&E).
"At some wards in Dewsbury there’s been an outbreak of the norovirus.
"It’s been particularly busy across the service. Hopefully with a nice patch of warm weather things will improve."
In February, it was revealed that around a fifth of people attending A&E in the local area were not being seen within the recommended four-hour timeframe, though almost patients with the most serious problems were treated imminently.
In a statement, the trust's director of operations, Trudie Davies paid tribute to staff for their work during the busy period.
She said: "We continue to see a high volume of people attending our emergency departments and urgent treatment centre, and in April we experienced our busiest month ever.
"Our focus continues to be on helping patients to leave hospital as soon as they are medically fit. To support this we have implemented therapy teams seven days a week at the Pontefract Stroke and Medical Rehabilitation Unit and at Dewsbury.
"The initiative, alongside very close working with colleagues in social care and community services, has played a key role in reducing length of stay.
"As always I’d like to use this as an opportunity to remind the public to choose wisely when they become ill.
"Emergency departments are for people with life threatening conditions such as strokes and heart attacks and emergencies such as broken hips, and severe infections.
"Walk-in centres, GP surgeries and pharmacies are the most appropriate place for conditions that are urgent but not emergencies.
"We also have our urgent treatment centre at Pontefract Hospital which treats people with non-life-threatening conditions.
"It’s really important people choose the right place to go, so we can ensure the emergency department staff are there for those who really need them.
"We did experience an outbreak of norovirus, which is now over, and are grateful for the amazing work of our nursing teams in looking after those patients."
Local Democracy Reporting Service