Belfast City Hospital has reported higher numbers of dehydrated elderly people and sunburnt youngsters as temperatures continue to soar.
A man seeks shade at Rose Week in Belfast's Lady Dixon Park
People have been advised to take precautions in the hot weather.
Registrar at the City Hospital emergency department, Owen Ferry, said people in Northern Ireland were not acclimatised to such heat.
However, the hospital had seen fewer cases than previous years as people took on board advice, he said.
The Met Office said Wednesday would be dry, very hot and sunny, but there would be thundery showers in the evening.
It said temperatures would be very hot over inland areas, but a touch cooler along the east coast, with a maximum temperature of 29 degrees celsius.
On Wednesday, Dr Ferry said: "We have noticed in the last week or two, with the warmer weather, there have been larger numbers of people coming in.
People have been advised to take precautions in the sun
"The typical sort of things we are seeing are younger people with sunburn, sometimes quite extensive sunburn, particularly round the face, the arms and legs.
"We have certainly seen some older patients who maybe haven't been dealing with the temperatures well and falling foul of dehydration.
"The heat has certainly been a factor in some of the conditions we have been seeing.
"There are more and more people heeding the advice that is being given out and we are probably not seeing the higher numbers we have seen in previous years."
He said it was important for people to stay out of direct sunlight during the warmest part of the day, wear a hat, apply high factor sun cream and wear long, loose clothing.
"It is a matter of being sensible... burn times can be as little as 10-15 minutes at times."