How much does humidity impact a race or workout?

about 50 seconds or 15%

A few calcs exist online to help adjust your pace per mile for Dew Point.

http://maximumperformancerunning.blogspot.com/2013/07/temperature-dew-point.html

I usually refer to this if I know it is going to be brutal hot/humid during a workout. Everyone is different though. Some people need more adjustment, others aren't as affected by the weather.

if the dew point is 84 i would just postpone tempoing

Let's go with 85/95. That's horrible, but it happens certain times of the day, certain times of the year, in certain parts of the country.

There are two effects.

The first is from the difficulty breathing. It typically isn't a factor in sprints or middle distance. But by the end of mile 2, you can tell you're breathing is in trouble. After mile 3 or 4, the full effect is felt, and the cost is real. I don't know the math, but from personal experience and from running with or coaching maybe a hundred others, I'd say it's 10% or more of a performance drop.

The second effect is from fluid loss or overheating. If you are a non-sweater, or an extremely light sweater, you can overheat. That might take 60+ minutes, depending on how hard you're going. If you are a heavy sweater, you probably won't overheat but sweat will pour off you like you're a garden hose. Your sweat rate can be so high that you can't replace it by drinking. You can't digest enough, quickly enough. With the massive drop in hydration will come a massive drop in performance, apart from breathing troubles. If your workout is under two hours, that might be ok, but if you push into hour 3, trouble...

The good news: If you train reasonably in high temp/high humidity, your body will adapt, and the adaptations will help tremendously in those conditions and in better conditions.

Some runners are figuring out that training in high temp/high humidity is as beneficial as training at altitude. Maybe more.

That's an 83 dew point which I've never actually seen in my life. Although, I think it can happen it certain parts of the world at certain specific times. A dew point over 75 affects your performance so much that anything other than a jog is very difficult. Dew point tells the story.

PTF wrote:

That's an 83 dew point which I've never actually seen in my life. Although, I think it can happen it certain parts of the world at certain specific times. A dew point over 75 affects your performance so much that anything other than a jog is very difficult. Dew point tells the story.

I live in Athens, Ga and in the summer if I run during the day(like a fool) it is at least 85° with 70+ % humidity. I expected the humidity to be higher all of the time but just checked the weather and it even gets down to around 60%. I sweat a ton during the summer, so much to the point that my shoes(and everyone I run with) will feel like I stepped under water after a run and it takes the rest of the day to dry.

John Clendon wrote:

A few calcs exist online to help adjust your pace per mile for Dew Point.

http://maximumperformancerunning.blogspot.com/2013/07/temperature-dew-point.html

I usually refer to this if I know it is going to be brutal hot/humid during a workout. Everyone is different though. Some people need more adjustment, others aren't as affected by the weather.

I don't know ...I feel like the vertical axis of that chart should be labeled humidity, not dew point. Doesn't seem right at all. Once you are at 70-75 dew point, running gets really tough, regardless of the temperature. And running in a 75 dew point and 75 degrees is virtually the same as running in 95 degs with 75 dew point...unless you are in direct sun.

Something's off...

PTF wrote:

That's an 83 dew point which I've never actually seen in my life. Although, I think it can happen it certain parts of the world at certain specific times. A dew point over 75 affects your performance so much that anything other than a jog is very difficult. Dew point tells the story.

Prior to this thread I've never even heard dew point mentioned. I just checked and it is currently 74 lol

TheRunningTroll wrote:

PTF wrote:

That's an 83 dew point which I've never actually seen in my life. Although, I think it can happen it certain parts of the world at certain specific times. A dew point over 75 affects your performance so much that anything other than a jog is very difficult. Dew point tells the story.

I live in Athens, Ga and in the summer if I run during the day(like a fool) it is at least 85° with 70+ % humidity. I expected the humidity to be higher all of the time but just checked the weather and it even gets down to around 60%. I sweat a ton during the summer, so much to the point that my shoes(and everyone I run with) will feel like I stepped under water after a run and it takes the rest of the day to dry.

That makes sense. 85 degs with "just" 70% humidity is a 74 dew point which is brutal. It's like running at altitude. I wouldn't be surprised if it slows you down 10%.

Even 85 degs with 60% humidity is about 70 dew point and that's tough.

TheRunningTroll wrote:

PTF wrote:

That's an 83 dew point which I've never actually seen in my life. Although, I think it can happen it certain parts of the world at certain specific times. A dew point over 75 affects your performance so much that anything other than a jog is very difficult. Dew point tells the story.

Prior to this thread I've never even heard dew point mentioned. I just checked and it is currently 74 lol

Ha ha...years ago...a knowledgeable fellow going by the name "malmo" clued us in to the dew point thing. You can probably search for it. He explained it really well.

High dew points are tough and they impact enryone differently, butnyou donadapt over time. I live inland in Central Florida and during the summer the dew point rarely drops below 70 and is almost always between 70-76.

The amount of impact is variable. It often impacts older runners more than younger. Bigger runners more than smaller runners. Then there is the adaptation that comes from running in high humidity and warm temps - increased blood plasma for those who train in these conditions.

So the idea that running hard is nearly impossible in dew points of 75 or so, and the idea that you will be impacted by 10% (going from say 5:20 tempo pace to 5:50 tempo pace) are overstatements for most people who train in these conditions regularly.

Yeah these running calculators definitely don’t take into consideration mild acclimation, which is a shame. Racing in a dew point of 70-75 is NOT something I can ever fully adjust to, even at the end of the summer. But I really don’t think I’m losing 5-10% at each end either.