If running at 50-60 deg F is ideal for a marathon in low humidity (RH < 60%) then what is the ideal temp for high humidity (RH > 60%) ?

Is it the same?

It is the same but the value is more like 40-45F not 60F. I was mentally stuck on a number of 60F that Ive heard about some long time ago, so I didnt even read the article close enough. My personal fastest times came with temps around 45F.

Loved the NOAA heat index provided by brentwpeterson; it was right on target. Once again I had a heat index table and some other methodology that didnt match up with what I was seeing. The NOAA heat index is spot on. My area is +95% RH nearly every morning and I definitely notice the ramp up in heat just above 80F. Plus the increase in heat index due to the sun and decrease due to wind is something Ive noticed as well. The impact on pace is dramatic, and for me at the time I wasnt drinking properly making it even worst.

One note for people reading this and trying to deal with humidity. From my experience short fast runs 3-4 miles doesnt have the same dramatic impact that longer runs have. My 5k speed is progressing evenly through all seasons and it definitely depends more one training than weather, so summer is for speedwork I guess and learning how to do the ultra shuffle for long runs.

1 Answer 1


Everyone body behaves differently to temperature and humidity, but you can look at the "Heat Index" If the heat index is high enough then you know that you will have to adjust your pace for the race.

For example: If you are running a Marathon at 90f and 90% humidity the heat index will be 122. If the temp is 80 and the humidity is 40% then the heat index is 80.


I don't think you will have a problem when the temp is lower than 70f. Most heat index chart start at 75-80f.

For the "Ideal" temp it is what your body can handle. The higher the temp and humidity the more you should adjust your pace.

  • Here in Florida there is almost always a high humidity of +60%. I noticed some of my fastest times were in the 45-50 degree weather which is alot lower than the ideal 60F. Lately in the morning its been about 75F and +90% RH in the morning and Im still sweating in huge amounts, and I know my pace is still affected. Some sources for pace impact due to humidity turn it into a binary thing with a threshold of 60%. Im wondering what (or if there) is an ideal temp for high humidity.
    – Jason
    Commented Sep 11, 2015 at 1:15
  • Since you can't control your environment it seems like a better idea to try to control your runs in the environment you are in. This would mean slowing down, making sure you are hydrating. You should eventually acclimate to your temps. Commented Sep 11, 2015 at 14:14
  • Adapting to humidity would mean 60F is the ideal temp, but I dont think you can fully adapt to this. When its humid sweat doesnt evaporate and you dont cool down. Cooling down is like one of the primary functions you need so its interesting to know if there is an ideal temp or not. Maybe it depends on thermal equilibrium so the ideal is not fixed?
    – Jason
    Commented Sep 11, 2015 at 20:18
  • @Jason I am not sure what you are asking? This is really specific to you and can't be quantified. Last night we ran in 85f with a 70 degree dew point. I toughed it out. I would suggest running on a treadmill when you don't feel good running outside Commented Sep 17, 2015 at 15:13
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    @Jason - If you read the article, it also shows difference in temperatures according to running speed and body size. They extrapolated from a very big sample, but it is still a guess. Everyone will have their own set point where they feel comfortable and perform best.
    – JohnP
    Commented Dec 9, 2015 at 18:11

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