Marathon pace training in high heat and humidity

run early or late

Go by effort.

Effort/heartrate.

Two things I make sure to do before my early morning tempo runs in humid conditions is drink 10-12 oz of Gatorade before heading out the door and wear a thin, breezy singlet (Saucony Inferno is what I have)- not sure what the female equivalent would be for the latter, if applicable. Doing these two things at least seem to help. And I agree to some extent with "go by effort": If you are in shape and are laboring with a pace you are usually comfortable with, humidity could very well be the culprit (there is plenty of info online regarding this topic including this:

http://runnersconnect.net/training/tools/temperature-calculator/

)

Hope this helps.

I never timed or measured anything on the roads so the weather did not matter. I ran very early or very late except for sessions that were for heat training. In those, I wore at least one track suite and ran at mid day since we raced in the mid day heat. We did not take water. My first marathon was on Labour Day and it was a very humid 92 degrees. I was very sick for a few hours after.

The morning is the best time for your sessions. It does have higher humidity but it's deceiving because humidity is based off the temperature. That's why the humidity goes down during the day, while temperatures rise. If you want to know how much moisture there really is, look at the dew point.

But like others say, run by effort. If you are trying to run marathon pace in really hot weather, it's probably much closer to your half marathon pace, which changes the nature of the workout.

They have all sorts of fancy calculators and conversions you can use but my usual rule of thumb is to add the temperature and the dew point together. If it's above 150, I slow down about 10s per mile (or more), 140s is 5-10 seconds, 130s is 5ish seconds or less.