As one of the hottest summers ever recorded drew to a close, Jay Portnoy watched patients stream into Children’s Mercy Hospital and Clinics in Kansas City, Mo., coughing and wheezing with asthma, 20 admissions per day for the week that started with Labor Day, he said.

They were coming in from what Portnoy, chief of the hospital’s allergy, asthma and immunology section, called a perfect storm — hot, dry air; low humidity; trees and plants that bloomed early; months of high pollen counts. An allergy bomb targeting the face and lungs.

“This past spring, people were having really bad eye problems” that physicians in his part of the country do not see that early, Portnoy said. “Usually it’s nasal, but now it’s the eyes.” Asthma cases normally show up at the end of September, he said.

Allergists are seeing illnesses earlier in the season after the third warmest summer on record in the Lower 48. Several studies have shown that the allergy season has grown longer because of global warming. At the end of this summer, allergists say they expect to have data to prove it is having a severe impact on the public.

Although emergency rooms are hopping and doctors are busy, they do not have hard data to show increased sickness from allergies is linked to the warming climate. No one has done a study to show that, said several state health officials and the directors of professional organizations.

But Portnoy is convinced that something weird is happening. “It’s been a secular trend, gradually getting worse,” he said.

“This year it all came together, warm in the winter, all the plants started producing their pollen,” Portnoy said. “My guess is probably it was a worse year than other years . . . because it was a perfect storm of hot, dry, low humidity.”

In the Washington area, pollen from elm trees spiked a month early, at the end of February and the beginning of March, and held at high levels through April, said Susan Kosisky of the Army Centralized Allergen Extract Lab.

That was followed by a variety of other trees blasting pollen well into May. The air was already full of pollen when grasses released another fusillade that peaked in June. Next up, ragweed.

“We had a lot of patients calling,” for a gamut of reasons, Kosisky said. One was the mix of pollens that stuffed noses day after day, rarely giving sufferers a break.

But it is not simply that more pollen is in the air, said David Peden, an allergist at the University of North Carolina. Americans are likely being exposed to a new super pollen. Studies have shown that plants treated with carbon dioxide and ozone emissions — causes of global warming — release a more potent pollen, with greater amounts of allergens per pollen grain, he said.

“When you’re consistently exposed to things you’re allergic to, you never give the nose and the lungs any real rest,” Peden said. “A person’s response to things they are allergic to can be increased by other things, like ozone, air pollution and associated climate-change issues. People who encounter it will be more sensitive.”

The result can be a tremendous drag on the workplace, with more and more employees reeling from allergy-related respiratory problems and headaches, leaving work early or being less productive. Ditto for students in schools.

“People tend to feel run down, [have] difficulty concentrating, [are] distracted at school, at work,” said Stanley Fineman, an allergist at the Atlanta Allergy and Asthma Clinic. “They have secondary complications like sinus infection, triggering asthma. I wouldn’t say it’s life-threatening. But there’s a condition called presentism, someone who goes to work and is not functioning the way they should.”

Summer’s dog days were highlighted by conditions that contributed to the respiratory distress. A prolonged Midwest drought increased dust levels, and wildfires that scorched nearly 4 million acres produced thick smoke, according to the National Oceanic and Atmospheric Administration.

It was bad enough to even walk in the summer of pollen, said Christopher Randolph, an allergist and immunologist in New Haven, Conn. Try running in it, like elite Olympic athletes who train outdoors.

“They are inhaling massive amounts of pollen,” he said. Climate change has affected the Olympics at least dating back to the Atlanta games in 1996, “all demonstrating enhanced pollination,” Randolph said.

As athletes train and compete, “they inhale about 200 liters a minute, massive amounts of airborne allergens,” he said. “It’s very concerning. It’s why we’re very aggressive about treating our athletes with inhaled steroids and nasal steroids.”

There is no question that elite athletes are suffering from more seasonal allergies, Randolph said — a finding that does not bode well for weekend warriors, either.

The growing reliance on albuterol by athletes to treat asthma has become such a concern that the world doping agency requires them to prove they have the illness.

The observations by doctors such as Peden, Randolph and Fineman are hobbled by a lack of definitive data. Scientists and doctors said they only knew of studies showing that global warming has prolonged the allergy season and supersized the pollen count; they knew of no studies that link warming to increased allergy suffering.

Daniel Ein, director of the Allergy and Science Center at the George Washington University School of Medicine, said there is no hard evidence showing an increase in emergency room visits for respiratory illnesses.

“You’d have to look at the emergency room statistics over a period of years. I don’t know of anyone who’s done that,” he said. “It’s bloody hard to prove. We’re busier than we were. This is always a busy time for us. We’ve been busy all year long . . . what’s that about I don’t know.”