Holy Heat and Humidity

j0439012Until this past winter I’d never really run in what I consider to be extremely cold temperatures (teens and low 20s and 30s). Most of my running has been in the spring through fall seasons in warmer temperatures and when I was in college in Charleston, SC, I had plenty of runs in hot and humid temperatures. So while I always thought I was a warm weather runner, by the time winter changed into spring this year I had definitely gotten used to cooler weather running. I wondered if I would welcome warmer temperatures the way I used to.

For some reason, this summer in Annapolis has been a slow build to the hot, sticky, humid temperatures we usually experience in July and August. Up until a week ago we had almost no humidity and temps were lingering in the mid-70s, still ideal running weather. All of a sudden though, full summer hit Annapolis with temperatures rising to the high 80s, 90s, and sticky humidity too boot. It didn’t take long for me to decide that I definitely prefer cooler weather running and there is no question that hot weather negatively affects my running performance. As much as I wish it weren’t true that heat affects running, an article in the August 2009 issue of Runner’s World details exactly why and how heat negatively affects running performance. Two weeks in a row I did a 1o-mile run early in the morning (both started before 8 a.m.). The first run I distinctly recall claiming to have been my best run ever when I finished. I had completed my 10 miles with an 8:45/mile pace and I was ecstatic. It had been 68° with no humidity and my average heart rate was around 152 with my max at 182. The next Saturday I left in the morning to run the exact same route. It was a steamy 78° and by the time I got to the last 1/2 mile in my neighborhood, which happens to include two killer hills, my legs were beyond heavy. My breathing was inconsistent, my form had crumbled, I felt tired, and after forging up the first hill I had to walk for a minute. I ran the second hill and had to walk. I finished the run at a horribly slow pace and saw that overall I averaged a 9:11/mile pace.  On that run my average heart rate was 155 and the max 185. Not a huge HR difference, but clearly higher.

j0289761Comparing those two runs is an obvious indicator of the negative affects of heat on running performance. Though the RW article acknowledges that this will happen it doesn’t negate the frustration I felt when I saw my two drastically different per mile paces for the exact same run. Advice for running in the heat focuses on staying out of the sun as much as possible and protecting yourself from the sun and heat while running. One tip is to cut mileage. Well, it’s tough to cut mileage when you’re supposed to be training and building mileage. Running earlier in the morning is great advice, if you can muster out of bed before the sun is up. I can do this, but not for multiple days in a row. Hydrating regularly is of course critical to running in higher temperatures, but overhydrating has its risks as well. I used to only use my fuel belt when I would run 13 or more miles and I think I’ve learned that when it’s hot, it can’t hurt to run with it no matter the distance.

While high temperatures aren’t ideal, I personally find humidity to be the bigger challenge. I find that when it’s super humid, my legs feel heavier than normal and breathing is harder. Taking a deep breath in humid air is nearly impossible. There is nothing to inhale that feels cleansing to my lungs and so I end up breathing quicker and more shallow. And when breathing becomes more work, my pace slows down. And the slower my pace, the heavier my legs feel. This was the point I reached on that hot 10-miler where the only thing I could do was stop and walk. As tempting as it was to try and power through I knew that I could only hurt myself if I didn’t give my body a chance to better recover with that one-minute walk.

Running in the heat will take practice. I am marathon training now and have at least another month of heat and humidity in front of me before it cools off. Knowing that long runs in the heat are not only difficult but potentially unsafe, I may find myself splitting daily mileage in two and doing half in the early morning and half in the evening. And of course, any advice you have on how to manage long training runs with heat and humidity is more than welcome!

I love summer and I will always prefer to be hot rather than cold, but when it comes to running, I am looking forward to cooler weather for the first time ever.

11 thoughts on “Holy Heat and Humidity

  1. Bill

    yeah, we’ve lucked out this summer in DC, but now that humidity is here, I think it requires, somewhat ironically, that you concentrate more on your mental state than physical one. Be happy with 3 miles instead of 5, or 6 instead of 10, or 20 miles a week instead of 30. And think, hey, that’s not bad for August around here. On the physical side, I’ve found that it helps to keep an eye on the weather forecast and hope for a break in the humidity and to time longer or faster runs to such. Even using a treadmill indoors can be tough this time of year but I’ve found it helps to maintain current pace. No thoughts on making up for long marathon-training runs but you have more time for Richmond than for Marine Corps at least.

  2. Srini

    Today, August 10, 2009 the weather in Newark, DE is been very hot (close to 84 degrees) and 85% humidity. Usually, I run 7.5 – 8.0 miles on alternate days. Today, I was able to run close to 2 miles and was very tied, problem with breathing and my legs were very heavy. Some how, during these two miles, I had to loosen my laces twice. I was trying to find the reasons for heavy legs and here it is ‘ Article by Natalie’.

  3. Natalie Post author

    @Bill, good tips for changing the mental approach. Somehow I completely forgot about treadmills. I get so anti-gym in the summer (though I go there to use the pool) that I completely forgot about the treadmill option which is a great alternative in high heat and humidity. Thank you!

    @Srini, I wouldn’t be surprised if the high heat and humidity is what contributed to your legs feeling heavy but if it feels that way consistently, I would definitely consult a professional coach or doctor as there could be more to it. It is frustrating though when you can run 8 miles one day and hardly 2 the next. Good luck with your training!

  4. mark lidman

    glad to hear I’m not the only one suffering as my 12 mile run saturday morphed into a slow 7 with the last mile a survival shuffle. found out weather was 70s and sunny with 97% humidity. Figured legs were tired from running days in a row, but now it might be the weather also. In a.m. humidity is highest but without sun might be manageable

    1. mark lidman

      well, damn. I was looking for advice on running in heat/humidity and found a post I put up 5 years ago!
      I guess it’s “good” that I had the same problem back then, but now I’m older and worse. Had to cut run today and stop a couple of times on a 70 degree cloudy day but humidity was 83%

  5. Natalie Post author

    Mark, you’re definitely not a lone! Humidity makes it tough all around. Typically mornings are better even if it’s still humid. I just read that this is in part because your core body temperature is lower first thing in the morning so even though it will still be hot and humid outside it will take your body a little longer to feel the effects. Either way, make sure you stay hydrated!

  6. Christina


    Thanks for the article! I’ve only been running seriously about 1 1/2 years but during that time I’ve seen a slow and steady improvement in my pace and miles logged on my long runs. I had a knee injury in the winter and spent the spring working myself back up to where I was. I felt I was on track again to try running my first 1/2 marathon later this year and then WHAMMO– hot weather and humidity arrived and my performance began to backslide. I guess I must be running more this summer than last because I am definately feeling more sluggish. Glad to know it’s just the weather and that I haven’t lost my mojo! LOL!

  7. Young Frank

    No doubt humidity is what gets me the most! I ran a fair amount in the 90+ degree temperatures in Alabama this summer (reached 100+ on a few days), and after about two weeks the heat never bothered me. I had done most of my running inside to build up and then try to take on the heat. I could always tell if it was humid though, as I would sweat a lot more and of course feel more sluggish sooner. I would take those 100+ degree days with lower humidity than upper 80s and high humidity any day!

  8. Febs

    I just finished the Bangkok marathon. Even with a 3am start I struggled with the heat, 25-26C with 80% humidity. I started conservitivley but by 35k had slowed to a crawl. I finished in 4.14 more than 40 mins outside my PB. Yet friends I was with seemed unaffected infact one guy got a 3.14 PB. We train in the same climate so why the huge difference?

  9. Natalie Post author

    Febs, congrats on what sounds like a great race despite the conditions! This summer I read an article in Runner’s World covering this same question. It’s frustrating to see what others do alongside you in the same conditions, especially when you’ve trained together and you know what you’re capable of. At the end of the day though the smallest things can make a difference in how you perform: weight, hydration, fuel, rest, stress, strength, form…the list goes on. And while it’s hard, try not to compare yourself to your friends. You can only ever do as well as YOU can do and it sounds like you did your best in Bangkok!

    1. Febs

      Thanks Natalie,
      My next marathon is on the 26th Dec in Northern Thailand. The Climate should be cooler and the humidity less so here’s hoping for a better run. Of course a lot will also depend on how much self-control I can show on Christmas day.


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