Changing seasons affect many people with Long COVID, myalgic encephalomyelitis, and other chronic illnesses, but not all in the same way. Research has a long way to go before it can explain the phenomenon.
Key points you should know:
- Chronic illness communities have long noted seasonal changes in the severity of their symptoms, a phenomenon sometimes called the “October slide.”
- Not everyone with Long COVID, ME, and other related diseases experience worsening symptoms in October; for some people, the fall and winter might come with an improvement.
- Doctors and researchers still don’t know what might be triggering seasonal shifts in disabling symptoms. A few studies validate the connection, but there are many variables at play.
- People with Long COVID and ME have found a number of ways to manage their fluctuating symptoms, no matter when in the year they occur.
For able-bodied people living in temperate regions of North America, October comes with a slew of seasonal associations. Corn mazes and colorful leaves, apple picking and sweaters, Halloween, and yes, pumpkin spice lattes.
But for some people with illnesses like Long COVID and myalgic encephalomyelitis (ME), the month has a different connotation — the dreaded “October slide,” a seasonal pattern of worsening symptoms and increased disability.
At least that’s what some people report. After talking to eight people from around the world who live with Long COVID and/or ME as well as healthcare providers who treat these diseases, I’ve come to find the reality is much more nuanced. From people with autoimmune diseases to those with infection-associated chronic conditions, seasonal weather changes clearly play a role in how people experience symptoms. But everybody is different, and so too are the environments they live in.
Jennifer Bell, a family nurse practitioner at the Bateman Horne Center who sees many people with Long COVID and related conditions at the clinic for infection-associated illnesses in Salt Lake City, Utah, had never heard of the term before I reached out. But she does have many patients who start feeling worse in late summer and fall.
“Usually it’s just sort of a global reduction of function and flare of symptoms,” Bell said. Some patients experience worsening mast cell activation syndrome, dysautonomia, and joint pain. “It’s like they go into a crash.”
But the exact reason for this exacerbation of symptoms is much harder to pin down. The weather is multifactorial: a mixture of temperature, humidity, and barometric pressure. The fall in the northern hemisphere also comes with an increase in respiratory illnesses and increased life stress from children going back to school and upcoming holidays.
Whatever the cause, people living with the diseases and those treating them agree: something is happening to their bodies that feels related to weather.
Stories of seasonal setbacks
Among the people I talked with for this story, there was an even split in terms of seasons that worsened their illnesses. Four of the eight match the October slide pattern, though their symptoms may not get worse exactly in October. Elizabeth Lefebvre, who lives in Chicago, links her slide to daylight saving time ending in November.
The other four people experience essentially the reverse, with fall and winter being the seasons in which they feel the best and spring harkening a deterioration.
This is true across continents and geographies. Catherine Appleby lives in Motueka, New Zealand, an area with high amounts of sunshine hours but relatively short summers. Her symptoms are the mildest in the summer, but as soon as the weather cools, she feels worse again — what she considers to be her baseline.
Camille Koffmann, on the other hand, lives in the U.K. and feels best in the fall and winter. The recent increase in heat waves across Europe and the U.K. have made her summers that much harder. It’s a pattern seen around the world, with rising temperatures caused by climate change exacerbating conditions, like postural orthostatic tachycardia syndrome (POTS), that often co-occur with Long COVID.
“In my younger years … I was the one who stayed out in the sun the most, soaking up every ray of warming light for as long as I could,” Koffmann said by email. Now people can’t seem to understand why summer is so hard on her. “Complaining of the popular season … just causes a wider gap between myself and already relatively distant people.”
This gap sometimes includes interactions with the medical system. Koffmann said her doctors have often dismissively interpreted her symptoms as a “preference” rather than true fluctuation of illness.
Other people I spoke with have had doctors who are more receptive to their experience, but those doctors still can’t offer any clear explanation.
Relatively little research has been done on the phenomenon, so clinicians can only speculate as to which factors in the seasonal shift might be causing such dramatic swings.
“I would really like to see research start looking at what is actually happening systemically in the body when these seasonal changes occur,” said Amy Mooney, an occupational therapist and the founder of OT4ME, who treats many people with Long COVID and ME.
“What is happening with blood flow and vascular regulation? What happens to heart rate, blood pressure, and orthostatic tolerance? How are mast cells responding to these environmental changes?”
Complaining of the popular season … just causes a wider gap between myself and already relatively distant people.
Camille Koffmann, whose symptoms worsen in u.K. summers
Many unanswered questions, with a few surprising insights
Bell, who works in Salt Lake City, Utah, at 4,300 feet above sea level, has noticed that virtually all her patients feel better when moving to lower altitudes. She referenced one 2025 Long COVID study where people were treated in hyperbaric oxygen chambers for 12 weeks and had an improvement in symptoms, though the study did not use a control group.
“If you think about what’s happening when the barometric pressure drops as a weather system comes in, it’s not unlike somebody going up to higher altitude,” Bell said. A person might have a normal blood oxygen reading on a pulse oximeter, but that measurement doesn’t take into account the pressure of dissolved oxygen in blood plasma. Lower air pressure decreases the amount of oxygen in the blood, so less gets into the body’s tissues. In other words, people might feel symptoms from lack of oxygen reaching their organs even though their blood oxygen levels are measured as “normal.”
There are slightly more data available on rheumatic diseases and weather. Research going back more than a decade suggests that temperature, barometric pressure, humidity, and hours of sunlight have some impact on diseases like rheumatoid arthritis (RA) and Lupus — but it’s hard to say what’s correlation and where causation comes into play.
For example, a 2020 study of 117 people with RA from Oujda, Morocco, found a significant increase in joint pain in the winter. The city is in the northeast part of the country, with cold winters and wet springs. But a 2019 nationwide survey from Japan of 12,839 people with RA found the highest symptom burden in spring and the lowest in fall — a reverse October slide. The study authors note that “Japan has a unique climate pattern in early spring known as san-kan-shi-on (three days of cold weather followed by four days of warm weather),” a result of high and low pressure systems moving through on a regular basis. Perhaps it’s this variability that causes worsening symptoms.
Chinese researchers took a different approach in a 2026 paper, sequencing the microbial life found in the fluid of swollen knee joints from people with RA. They found that the species of bacteria changed from winter to fall — but what this means, and if it really is caused by the changing seasons, remains to be seen.
As for ME and Long COVID, only a handful of studies have tried to pin down the links between weather and these illnesses as well as related diseases, like fibromyalgia. A study from 2024 that looked at 58 women with ME in the Birmingham, Alabama, area showed that weather conditions that increased levels of air pollution were most correlated with worsening symptoms — not temperature, daylight hours, or barometric pressure. Even when air pollution levels were generally considered acceptable, patients still reported more symptoms on days with worse air quality.
Chloe Lisette Jones, a doctor of clinical neuropsychology and one of the authors of that study, said she was surprised to see such a strong signal between air quality and self-reported measurements of pain and fatigue. She also said she’s worried that with climate change, there will be more extreme weather fluctuations and natural disasters that will increase the vulnerability of sick and disabled people.
“It’s not a positive trajectory,” Jones said.
This research points to the complex array of factors at work in our bodies and our weather systems, something that Lara (who asked to be identified only by her first name for medical privacy) is familiar with. As someone with ME and Long COVID who studies the impacts of toxic mold and experiences symptoms from exposure, she has found her health takes a downturn in the fall when outdoor molds may be changing or interacting with other dangerous chemicals in the environment.
Alexis Misko, who has ME and dysautonomia, feels better in the winter (she lives in Ohio). She noted that the constant noise of lawn mowers and other yard equipment during warmer months “chip[s] away at [her] level of function.” On the other hand, Lefebvre, who feels worse during Chicago’s frigid winters, attributes some of this to the added energy requirements of scraping snow and ice off her car, battling cold winds, and walking through snow.
Chloe Lisette Jones … said she’s worried that with climate change, there will be more extreme weather fluctuations and natural disasters that will increase the vulnerability of sick and disabled people.
Surviving the seasons
Regardless of what weather affects them most, everyone I spoke with had specific strategies for getting through their own slide. Those who do better in cooler, darker weather set up light-blocking curtains and comfortable dark spaces they can retreat to. For those who struggle more in winter, getting extra sleep, wearing more layers, and the liberal use of heated blankets helps to a certain extent.
Anna Cechony, who has Long COVID, among other related diseases, lives in Seattle, Washington. She’s one of the few people I spoke with who learned of the October slide from her doctor. Cechony realized the term perfectly fit with her experience of symptoms growing worse in October. Now she plans ahead by making sure she’s stocked up on medications and meal prepping so she has nourishing food on hand, and she always takes a week off work in October.
Cechony plans an entire year in advance, she said — she scheduled her 2026 week off in October 2025. “I have no plans, but I can do friend stuff if I’m up for it.”
Graeme Seabrook, who lives in the Denver, Colorado, area, follows a similar strategy of lightening her workload during the most symptomatic months — for her, June, July, and the beginning of August. Because she runs a virtual business, she makes plans for low-effort summer activities earlier in the year.
Some people have even moved or traveled to be in environments that are more supportive of their bodies, and have seen a marked improvement in function. Appleby, who lives in New Zealand, felt much better when on vacation in the warm weather of Fiji. Jessica Dye, who lives near Austin, Texas, noticed an improvement of their symptoms when they were living in Ireland. The fall weather in Texas also offers a reprieve. They said their doctor encouraged them to move north for cooler weather.
“But that’s far easier said than done,” Dye said by email. Not only is there the financial burden to consider, as well as potentially leaving a support network, but the physical work required to move might trigger post-exertional malaise for those with ME.
Both Bell and Mooney work with their clients to help them plan for these shifts in weather in advance.
“The goal is not to control the weather,” Mooney said. “[It’s] to understand the person’s response, recognize when their capacity may be reduced, and adjust the demands around them so that this uncontrollable stressor is less likely to push their total exertional load beyond what their body can manage.”
[The goal is] to understand the person’s response, recognize when their capacity may be reduced, and adjust the demands around them so that this uncontrollable stressor is less likely to push their total exertional load beyond what their body can manage.
Amy Mooney, Occupational Therapist
Lorraine Boissoneault is a science and history writer based in Chicago. Her book Body Weather: Notes on Chronic Illness in the Anthropocene looks at the links between illness, the environment, and severe weather. You can follow her on Bluesky, Substack, and Instagram.
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