Humidity vs. temperature (and sunshine)

[CarolynFH]

This is a question for you experts in exercise physiology (and I've read enough posts on this board to know you're out there!). I live on the Gulf Coast, where we deal with high humidity year round (and not with those horrible cold wind chills y'all get up north!).

Is it better to run/exercise walk early in the morning when the humidity is high but the temperature is low(er), or later in the morning/afternoon/evening when the humidity is lower but the temperature is higher (and the sun is brighter and higher in the sky)?

For example, this morning at 7:00 AM the temperature was 71 and the humidity was 83% (that was low! Yesterday morning it was 68 and 95%). Three hours later it's 75 and 73%. Which would be a better time to get out there?

 

[DopeyBadger]

I am not an exercise physiology expert, but I'll add my two cents.

I personally use Temperature + Dew Point to assess training conditions.

71 + 83% Humidity is a dew point of 66. This gives a T+D of 137 (71 + 66).
75 + 73% Humidity is a dew point of 65. This gives a T+D of 140 (75 + 65).

So even without considering the sunlight the 7:00am T+D is better at 137, than the 10am at 140 (lower is better). This assessment of T+D gives me the "what does it feel like" consideration behind temp and dew. The lower the T+D the better. Anything in the 100 range for T+D is ideal. Anything above 160 becomes fairly intolerable for me.

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

Now, you added a twist by adding in the sun. The sun also provides a variable of solar radiation. On it's own solar radiation can effect a run by raising the temperature of the skin. While current research hasn't found a connection to many of the other associated variables (Heart rate, sweat rate, blood flow and core body temperature) the increase in skin temperature does effect performance. These other variables are effected by the T+D. Dependent on the level of cloud cover and where you live, there are varying levels of solar radiation.

So if in your case the T+D of the morning run (137) is lower than the mid-day (140) and no/little sun (because morning), then the easy choice is morning. The issue would be if morning T+D is higher than mid-day T+D with sun. Dependent on the amount of cloud cover, I'd still venture a pure guess that anything within 10 points of T+D (like 150 vs 140 with sun) is probably still better without the sun. But that's a pure guess as I have yet to find a calculator that takes into account solar radiation.

I really like this guy's set of heat calculators:

https://fellrnr.com/wiki/Heat_limited_running_pace
https://fellrnr.com/wiki/Perceived_Temperature_For_Runners_Version_2
https://fellrnr.com/wiki/Running_Heat_Model
https://fellrnr.com/wiki/Optimum_Running_Temperature

Here are some links about solar radiation effects.

http://www.slowtwitch.com/Training/Solar_Radiation_on_Performance_5870.html

http://www.runnersworld.com/sweat-science/how-much-does-sunlight-slow-you-down

https://www.ncbi.nlm.nih.gov/pubmed/26842928

Does this help?

 

[CarolynFH]

Wow @DopeyBadger, yes it does! I would never have thought to consider dew point. I'll follow the combination of T+D through a few days to get an idea of how it changes. My instinct has been "earlier is better" but there are mornings when the air is too heavy with moisture to breathe!

 

[The Expert]

Ugh, I don't even want to think about any of this. I train in the desert climate of Utah and heat+humidity is my enemy. I just hope my altitude advantage helps balance the scales!

 

[gjramsey]

Living in Houston, we have the same thing most of the year. I usually run pre-dawn, and yes, the humidity sometimes is very think. This past summer, I ran some late afternoon/early evening runs, and sweat less, even though it was mucho hotter out than early morning, since the humidity (and dew point) was so much lower. YMMV

 

[John VN]

I am not an exercise physiology expert, but I'll add my two cents.......................
Does this help?

IMO, an outstanding reply. Worth far more than "two cents."

 

[CarolynFH]

IMO, an outstanding reply. Worth far more than "two cents."

Yeah, DopeyBadger may not be an "expert" but he definitely has expertise!

 

[DopeyBadger]

IMO, an outstanding reply. Worth far more than "two cents."

Yeah, DopeyBadger may not be an "expert" but he definitely has expertise!

Thanks guys!

I'll add one more consideration (variable) @CarolynFH. Why are you training?

-If you're training for the purpose of getting fit, losing weight, exercise in general, then choosing the time of day with the lowest amount of solar radiation and T+D is ideal. It just makes it more comfortable to run.

-If you'e training for a specific race, then the ideal temperature during the day may not be the best time to train. I personally evaluate my goal race's history to determine what race day weather conditions will be like. I use Weather Underground. Under the name of the city is a "History" tab that allows you to choose any day from the past several years. In addition, once you choose your historical race day (for instance a race in New Orleans on May 6th) then I would go through the last 5 years of data to determine what the race day conditions are like. Once you choose a historical date, you can scroll downwards to get hour by hour conditions for both temperature and dew point. It's a really nice feature. Use the last 5 years of data to make a reasonable guess range as to what race day will be like.

Like this:



I was making a choice between these two races (DoLittle and Lakefront). I was trying to evaluate the historical T+D on the day and time of the race to see whether either had an advantage over the other. Lakefront won easily even though they're only separated by one week (more T+D in the 100 or less).

Once you know what the historical weather is like on race day, that's an important consideration for training. The closer you get to race day the more and more you want to make sure you're training in similar conditions. So if your race is May 6th in New Orleans (made up) and the typical T+D is 155, then when I'm making choices about time of day training for that race and I have morning at 120 and afternoon at 155 I should choose the 155. The body undergoes physiological adaptations to environmental conditions. So training in 155 T+D will make you a better runner at 155 T+D. If you consistently train at 120 T+D and race day is 155 T+D, then race day is likely not to go as well as training would indicate. The currently held scientific understanding is it takes about 14 days or 10 workouts to adapt to a new environmental condition. So the last two weeks before race day become hyper critical to not avoiding the non-ideal T+D if that's what race day will be like.

So the adage I use when training for a specific race is, "You never know what race day will be like, so train in all safe environmental conditions."

Hope this helps!

 

[CarolynFH]

Thanks guys!

I'll add one more consideration (variable) @CarolynFH. Why are you training?

-If you're training for the purpose of getting fit, losing weight, exercise in general, then choosing the time of day with the lowest amount of solar radiation and T+D is ideal. It just makes it more comfortable to run.

-If you'e training for a specific race, then the ideal temperature during the day may not be the best time to train. I personally evaluate my goal race's history to determine what race day weather conditions will be like. I use Weather Underground. Under the name of the city is a "History" tab that allows you to choose any day from the past several years. In addition, once you choose your historical race day (for instance a race in New Orleans on May 6th) then I would go through the last 5 years of data to determine what the race day conditions are like. Once you choose a historical date, you can scroll downwards to get hour by hour conditions for both temperature and dew point. It's a really nice feature. Use the last 5 years of data to make a reasonable guess range as to what race day will be like.

Like this:

View attachment 219186

I was making a choice between these two races (DoLittle and Lakefront). I was trying to evaluate the historical T+D on the day and time of the race to see whether either had an advantage over the other. Lakefront won easily even though they're only separated by one week (more T+D in the 100 or less).

Once you know what the historical weather is like on race day, that's an important consideration for training. The closer you get to race day the more and more you want to make sure you're training in similar conditions. So if your race is May 6th in New Orleans (made up) and the typical T+D is 155, then when I'm making choices about time of day training for that race and I have morning at 120 and afternoon at 155 I should choose the 155. The body undergoes physiological adaptations to environmental conditions. So training in 155 T+D will make you a better runner at 155 T+D. If you consistently train at 120 T+D and race day is 155 T+D, then race day is likely not to go as well as training would indicate. The currently held scientific understanding is it takes about 14 days or 10 workouts to adapt to a new environmental condition. So the last two weeks before race day become hyper critical to not avoiding the non-ideal T+D if that's what race day will be like.

So the adage I use when training for a specific race is, "You never know what race day will be like, so train in all safe environmental conditions."

Hope this helps!

Thanks again! Right now I'm just in the lose weight/get fit mode, but if/when I decide to enter a race I'll remember this!

 

[PrincessV]

<--- west coast of FL runner. I can say anecdotally that my early morning summer runs in lower temps ("low" being 80-85) and high humidity feel about the same as sunset runs in temps near 100 but lower humidity. In both cases, being in the dark or in shade makes it bearable (barely). Either situation plus full sun has fast and really unpleasant effects on my body. I'll assume dew point plays some part, but honestly - by August all I know is that it's HOT, it's been HOT for months, and it's still going to be HOT for months to come and I no longer care what the temp/humidity/dew point are lol!