The Dew or Dew Not Point

The 9th of June has a rich history of world-altering events. In 1934, Donald Duck made his film debut in the Walt Disney cartoon The Wise Little Hen. In 1999, The Federal Republic of Yugoslavia and NATO signed a peace treaty, officially bringing an end to the Kosovo War, and in 2020, SpaceX successfully launched its first crewed spacecraft, carrying NASA astronauts to the International Space Station. Though these are historical events, they pale in comparison to what I personally accomplished on June 9th, 2026 - finishing a 7-mile “easy run”.

What was supposed to be an easy trot along the trails turned to an incredibly difficult sweat-fest for the first five miles, and the final two in a torrential downpour. The reason? An 83 degree, 83% humidity day, a Dew Point of 73 degrees, and a catastrophically incorrect weather forecast (meteorology is just astrology for earth scientists). Horrific. I’m a heavy sweater as-is, but in these conditions my clothes are fully saturated within the first 15 minutes of the run. The only other times I am ever this sweat-soaked is every time I’ve ever talked to a pretty girl.

“Wait, Brandon. I’ve never heard of Dew Point” you may say. So let’s check it out:

Typically, when runners check the weather before a workout, they often look at the temperature and humidity. While humidity is important, there is another weather measurement that often has a bigger impact on how comfortable you feel while running: dew point.

What is humidity? Humidity is the amount of moisture in the air compared to the maximum amount of moisture the air can hold at a given temperature. It is usually reported as a percentage.

For example:

• 50% humidity means the air is holding half of the moisture it could potentially hold.

• 100% humidity means the air is completely saturated with moisture.

The problem with using humidity as a metric for running comfortability is that it changes based on temperature. Air can hold much more moisture when it is hot than when it is cold. This means a humidity reading alone does not always tell you how uncomfortable the conditions will feel. A day with 80% humidity at 50°F may feel pleasant, while 80% humidity at 85°F can feel oppressive.

What is Dew Point? Dew point is the temperature at which air becomes fully saturated and water begins to condense into dew. Unlike humidity, dew point measures the actual amount of moisture in the air. Because of this, many endurance athletes consider dew point to be a much better indicator of how muggy and uncomfortable conditions will feel. The higher the dew point, the more moisture is in the air.

So why does Dew Point matter? Your body cools itself primarily through sweating. When sweat evaporates from your skin, it removes heat and helps regulate your body temperature. When dew points are high, the air is already filled with moisture so sweat cannot evaporate as efficiently, making it harder for your body to cool itself. As a result, your heart rate rises, your perceived effort increases, fatigue occurs more quickly, and pace must be adjusted. A whole mix of confidence-killing conditions. The only other time I suffer such confidence-killing conditions is every time I’ve ever talked to a pretty girl. Not fun!

It is incredibly important to check this metric prior to getting outside for your summer runs. Not just from a safety perspective, but to anticipate the challenging nature of high-dew point days. You will need to adjust your pace and hydration accordingly, and may need to move your run indoors if the conditions are brutal enough.

“It’s possible for weather to be so oppressive a treadmill is a more desirable option?” you ask?

“Yes!” I’d reply.

Picture yourself in your funky-color-schemed gym at which you are a member. Take in the stale air, the refreshing scent of industrial strength disinfectant, eyes bouncing between that farm lady on Food Network and one of the 24-hour news stations that pump you full of feel good (definitely not anxiety-inducing) stories, or the thrill of finding a parking spot within a quarter mile of the entrance. For me, conditions have to be BRUTAL brutal before I opt for a treadmill, but it has been necessary plenty of times before.

Anyway - here’s a great chart from Runner’s World that shows what you can expect at different Dew Points:

DEW PT (°F) PERCEPTION HOW TO HANDLE

50–54 Very comfortable Great running conditions. No adjustments necessary.

55–59 Comfortable Hard efforts likely not affected

60–64 Uncomfortable for some Expect race times to be slower than in optimal conditions

65–69 Uncomfortable for most Easy training runs feel OK but difficult to do hard efforts

70–74 Very uncomfortable Expect pace to suffer greatly

75+ Oppressive Skip it or dramatically alter goal (AKA - Treadmill)

It’s easy to become frustrated when you cannot hit your usual pace and your usual heart rate zone during the summer months, but usually, fitness is not the issue.

A run at an 8:30 pace in cool, dry conditions may require the same effort as a 10:00 pace when the dew point climbs into the 70s. So instead of focusing on pace, focus on your heart rate and rate of perceived effort. Accept your slower pace, don’t let ego get in the way of safety, and hydrate properly. If you experience dizziness, chills, nausea, or loss of coordination, end your workout and find a place to cool down. Note: the best mid-run cooling method in humid weather is ice. Ice packs placed on your head, neck, arms, and mid-section will be your best bet. You may see runners pouring water on themselves to cool down, but that is only effective in dry conditions. The cooling occurs when the water evaporates from your skin, which does not happen in high humidity.

Remember, training adaptations still occur even when you run slower due to environmental conditions.

The Bottom Line:

Humidity gets all the attention. Taking the blame for everyone’s inability to enjoy their family vacation to Orlando in August because their cousin is still in high school and their aunt and uncle didn’t want to take him out of school to visit at a more comfortable time of year. So instead of being comfortable, they have to see Hogwarts at Universal Studios with their shirt stuck to their back, and even get to visit the ever-exciting American Adventure experience at Epcot just to get some air conditioning and falling asleep before the experience starts.

Perhaps that was more personal than I wanted to get, but the point is - dew point is the real monster here, not relative humidity.

Don’t be afraid of running outside during the summer. Before your next run, don’t just check the temperature. Look at the dew point as well. Understanding this can help you adjust your pace, train more effectively, and stay safe during the warmer months. On extremely oppressive days, you may even find me in your local gym. I’ll be the one yelling “NOTHING NEEDS THAT MUCH BUTTER!” at the farm lady on Food Network.

Now you’ll have to excuse me- I need to go inside and change out of sopping-wet sweat clothes. My pretty neighbor just said hello to me.

Stay smart out there.
Brandon