Weather can really mess us up.
We can train hard, have everything right, and then at the last second, a weather change can make our entire race plan go down the toilet.
Humidity is definitely one of those bad weather situations that can cause a drastic decline in performance.
BUT, before I go on, I hope you will consider the effort scale for running, this is the only way to guarantee you will run your absolute best race, no matter what the weather. This will mean you never have a BAD race again.
Sure, you will have days your time is slower than you hope, but if you follow my effort scale for success, you won’t ever be able to say anything bad about your performance, because you gave it your all.
In the summer, humid conditions make training rather difficult.
Most of us have run in humid weather at some point, and running in humid conditions can be miserable, but many runners do not consider the effects humidity will have on your body when exercising.
The dew point on humid days is usually significant and needs to be considered, as you can put your body in extreme danger through overheating.
How does dew point affect running?
Dew point is defined by the Dictionary of Environment and Conservation as “The temperature at which water vapour in air will condense on a cool surface and form drops (dew). This is the temperature at which a parcel of air would become saturated if it were cooled with no change in the amount of moisture it contained or in the atmospheric pressure.”
In English please?
As the dew point rises, and the air becomes more saturated with water, it becomes harder for your body to cool down as the sweat cannot evaporate off your skin.
This means your body has to work much harder to keep your internal temperature constant. This is why it is especially uncomfortable on days when it is humid, hot, and there is no wind because your body struggles to cool itself.
How much does dew point slow you down?
If you continue to push through at the same effort level you usually would, without the regulation of your temperature, your body will function only to maintain the temperature of your vital organs by directing its energy away from your muscles.
This is why you may feel cold sometimes after a race on a humid day as your body is confused and not working properly. This is a serious sign of overheating.
When you check the weather before a run, look at the dew point and humidity.
The closer the humidity is to 100%, the more it is going to affect you. The higher the dew point, the more that will also affect you.
Running Times created this chart on how you should adapt your training based on dew point:
| DEW POINT (°F) | RUNNER’S PERCEPTION | HOW TO HANDLE |
| 50–54 | Very comfortable | PR conditions |
| 55–59 | Comfortable | Hard efforts likely not affected |
| 60–64 | Uncomfortable for some people | Expect race times to be slower than in optimal conditions |
| 65–69 | Uncomfortable for most people | Easy training runs might feel OK but difficult to race well or do hard efforts |
| 70–74 | Very humid and uncomfortable | Expect pace to suffer greatly |
| 75 or greater | Extremely oppressive | Skip it or dramatically alter goal |
How does humidity affect people differently?
Unfortunately, studies have found that all unfavorable weather conditions affect slower runners more than faster runners due to the speed assisting with the evaporation of sweat.
They also affect female runners more than males due to the larger ratio of surface area to body mass combined with the slower overall speed.
This means that humidity does not affect everyone the same, and it can be difficult to make suggestions for everyone.
One study featured in PLoS One analyzed the results of six of the biggest marathons in the world (Paris, London, Berlin, Boston, Chicago, New York) in a long term study covering 1, 791, 972 participants from 2001 to 2010.
They found that humidity had a high impact on performance, and was significantly correlated with a drop in performance levels.
How should I change my pacing/time goals in humid weather?
Do not panic if you feel fatigued when it is humid. It is normal to feel as though you are working much harder, as your body is reacting to the stress it is under, and will be unable to dedicate as much energy to your muscles performing at their best.
Keep the chart shown above in mind when you are training in humid conditions.
On these days, from my experience, it is best to run by effort level.
Have a rough indicator of the pace you would like to run at, but go based off the feel. You should be able to tell if you are going too fast through your breathing and perceived effort.
I would recommend not looking at your GPS watch for the entire duration of a workout. Keeping in mind that the reason you feel bad is not because you are out of shape, but because your body is working hard to stay cool.
This is also a great time to use your heart rate to make sure you stay within your limits.
Runners World wrote a great article with tips for running in humidity, but this is the most important part:
Be mindful of the early warning signs of heat exhaustion and heat stroke: fatigue, nausea, dizziness, headaches, tingly skin, and confusion.
Call it quits if you experience any of them—even if you haven’t reached the end of your run or the finish line yet. It is better to be safe than sorry.
Does running in humidity get easier?
If you continue to train in humid conditions, your body will learn to adapt after two weeks. As your body gets used to the humidity, it will acclimatize and get easier.
You will need to consume A LOT more water and electrolytes than you usually would; before, during and especially after working out.
What else do I need to consider when running in humid weather?
Humidity is often called the “poor mans altitude”, in the way that your body reacts to it.
Humidity should be treated as serious as running in altitude, and the adjustments should be similar.
Remember, it is critical to ensure you are consuming enough water, and replenish with electrolytes after. Enduropacks have a great spray for adding to any drinks. I carry it in my shorts during my marathons, so that is how much I believe in it.
This is when the pee test comes in especially handy. This means that you should continue to drink water until your urine is very pale yellow.
The biggest indicators of dehydration are dark urine, and an elevated heart rate.
One way to know roughly how much water to drink is to weigh yourself before and after your run. The difference in weight, is how much water you need to consume (16oz water in a pound).
