Published August 27, 2026 01:57PM<\/p>\n<\/div>\n
One day in July, I woke up to a rare summer treat: a crisp 67-degree morning. Ready to take advantage of the cooler weather without battling the smoke, rain, or extreme temperatures plaguing New York City this season, I set out with high hopes. But within a few blocks, my optimism had evaporated, as the humidity left me struggling to maintain a pace that should have felt easy.<\/p>\n
In the end, I cut the run short, feeling more than a little discouraged by my performance and the day\u2019s turn of events. It was the sort of run you\u2019d expect during a heatwave, not on an unseasonably cool(er) day.<\/p>\n
To get a better understanding of what went wrong, and how to avoid another miserable run, I turned to the experts who explained why high humidity levels are so hard on the body and how to best adapt your training during the muggiest months of the year.<\/p>\n
How Humidity Affects the Body<\/h2>\n
The main thing I wanted to understand was why my sticky Saturday morning jog wound up feeling as draining as a marathon.<\/p>\n
So I turned to John Gallucci Jr., DPT, and CEO of JAG Physical Therapy<\/a>. Gallucci is a physical therapist and expert in sports medicine, the associate chief medical officer for Major League Soccer, and has worked with professional athletes all over the Northeast, where humidity levels often impact training and performance.<\/p>\n \u201cHumidity changes how efficiently the body can regulate its internal temperature,\u201d he told me. \u201cWhen we exercise, our bodies rely on sweating as the primary cooling mechanism, and the evaporation of sweat is what lowers body temperature.\u201d<\/p>\n \u201cIn humid conditions, the air is already saturated with moisture, making it much more difficult for sweat to evaporate,\u201d he explains. \u201cYour body retains more heat, your core temperature rises faster, and your cardiovascular system must work harder to circulate blood to both the working muscles and the skin to facilitate cooling.\u201d<\/p>\n In other words, humidity can turn an otherwise easy run into a much harder workout.<\/p>\n \u201cFor runners, this often translates into a higher heart rate, quicker fatigue, an increase in perceived exertion, and a noticeable decline in pace,\u201d he says. \u201cA run that would normally feel comfortable can feel like a much more intense workout in humid conditions, even if the distance and effort haven\u2019t changed.\u201d<\/p>\n One way to account for humidity\u2019s impact is to adjust your pace accordingly. But how much slower should you actually run?<\/p>\n Chris Minson<\/a>, professor of human physiology and co-director of the exercise and environmental physiology labs at the University of Oregon, told me there are \u201cno specific pace recommendations that can be made as both heat and humidity can greatly impact athletes in different ways.\u201d<\/p>\n However, at higher humidities (those upward of 75 percent relative humidity), he suggests slowing your average pace by at least ten seconds.<\/p>\n \u201cOnce [runners] are much too hot, it is hard to back off enough to recover, so it is better to start on the easier end,\u201d Minson says.<\/p>\n Gallucci emphasized that humidity\u2019s negative impact on the body doesn\u2019t mean you can\u2019t<\/i> run outdoors when humidity levels are high, or even that it will always feel like a drag.<\/p>\n \u201cThe body can adapt to humid conditions over time,\u201d he told me. \u201cYour body is adept at getting used to the heat if you give it some exposure. Gradually training in warm, humid conditions allows the cardiovascular and thermoregulatory systems to become more efficient, improving heat tolerance in as little as one to two weeks.\u201d<\/p>\n \u201cHowever, even for those acclimated to heat and humidity, runners should respect the environmental conditions and recognize that humidity is a legitimate performance factor that isn\u2019t a reflection of their conditioning,\u201d he cautions.<\/p>\n Minson largely agrees, but says he prefers runners \u201conly do some training in a humid environment and focus on good adaptation to heat.\u201d<\/p>\n This approach, he says, will improve overall thermal tolerance, help lower heart rate and core temperature at a given exertion and environmental temperature, and reduce perception of effort. In the end, training in a combination of heat and humidity may help runners acclimate to humid conditions more quickly.<\/p>\n <\/p>\n Thanks to climate change, the odds of running a humid marathon are increasing each year. \u201cFor recreational runners\u2026the odds of racing in cool, optimal temperatures are already slim (27% on average)\u2014and likely to shrink with future warming,\u201d a report from Climate Central<\/a> found.<\/p>\n That being said, there are some major races that are already well-known for their high humidity levels. Below is a list of the 10 most humid marathons, according to data from FindMyMarathon.com<\/a>.<\/p>\nHumidity\u2019s Impact on Your Speed<\/h2>\n
The 10 Most Humid Marathons<\/h2>\n