We all have preferences when it comes to what we consider to be the best weather for various activities like going to the beach, taking a hike, or having a picnic in the park.
But what is the perfect running weather? Is there a best running temperature or an optimal running temperature and humidity for performance?
Hot and humid weather can have an effect on our running for sure, but just how much slower do we run if the temperature is hotter than the ideal marathon temperature?
In this article, we will discuss whether there is “perfect running weather,“ what the ideal marathon temperature is, and the physiological challenges of running a marathon when it isn’t the optimal running temperature.
We will cover the following:
- What Is the Ideal Marathon Temperature?
- What Happens When It’s Hotter Than the Ideal Marathon Temperature?
Let’s get started!
What Is the Ideal Marathon Temperature?
After a cold winter, when you get to enjoy some of the first warm, sunny spring days, you might remark to your running buddy, “This is the perfect running weather!“
But, is there such a thing as “perfect running weather”?
Most runners and exercise physiologists would agree that when the day is dry with no precipitation and very still winds or just a slight breeze, the weather conditions would be considered much more along the lines of “perfect running weather“ than if it is very windy, raining, sleeting, snowing, hailing, or thunder storming.
Essentially, there should be no precipitation, and there should be little to no wind when you have a perfect running weather day.
Wind will slow you down because it will create a headwind at some point in your run unless you are running from one point to another along a long straight road where the wind will always be at your back.
Precipitation is uncomfortable in most cases and can also slow you down.
It can compromise visibility, temperature regulation, footing, and can saturate your clothes and shoes, which will wear you down and can cause blisters, give you the chills, among other uncomfortable sensations.
But, a major factor that plays into the “ideal running weather“ is the temperature. So, is there an optimal running temperature or an ideal marathon temperature?
One study compared the results of six marathons based on four environmental factors: temperature, humidity, dew point, and the atmospheric pressure at sea level.
The air temperature was found to have the most significant effect on running performance and dropout rates of runners of all levels, while humidity affected faster women and men only.
The more the air temperature increased above the “optimal running temperature,” the slower the running speeds and the higher the withdrawal rates became.
The best temperature for marathon running—which was the temperature where runners ran the fastest—for each performance level was as follows:
| Performance Level | Ideal Running Temperature for Men (°F) | Ideal Running Temperature for Men (°C) | Ideal Running Temperature for Women (°F) | Ideal Running Temperature for Women (°C) |
| Elite Runners (top 1% of runners) | 38.9 | 3.81 | 49.8 | 9.91 |
| Top Quartile (top 25% of finishers) | 42.8 | 6.02 | 44.3 | 6.85 |
| Median | 43.2 | 6.24 | 44.1 | 6.75 |
| Third Quartile | 45.4 | 7.42 | 45.2 | 7.35 |
These results suggest that the best temperature for running for most runners is around 5.9°C or 42.6°F for men and 7.7°C or 45.9°F for women.
A separate study that looked at the relationship between Boston Marathon race results and the weather on race day found that the optimal temperature for marathon performance is between 44° F and 59° F (7–15° C), though the best results occur at wet bulb temperatures below 7.8 °C (46 °F).
There was a fairly linear relationship of slower average finish times for each additional 1 °C increase in temperature above the ideal marathon temperature.
What Happens When It’s Hotter Than the Ideal Marathon Temperature?
More often than not, you won’t get “perfect marathon running conditions“ on the day of a marathon or long run, so what physiological consequences occur when it is hotter than the best temperature for running marathons?
The first hydrological response to running in the heat is that you’ll start sweating sooner and more heavily than when running in optimal marathon temperatures.
Sweating is really only effective at cooling down your body temperature in the sense that the excess heat energy is used to help evaporate the moisture that builds up on your skin in the form of sweat.
The heat energy is released as it is used to transform the phase of matter of sweat from liquid water to vapor.
By helping evaporate the sweat off of your body, heat energy is dissipated, dropping your core temperature down.
However, when it’s humid, the moisture content in the air prevents sweat from evaporating readily, so the perfect running weather not only involves the ideal temperature for marathon running but also a relatively dry day with low humidity.
Running in the heat also increases cutaneous blood flow (blood flow to the skin) to help dissipate excess heat.
This can reduce blood flow to your muscles, which may make your run feel tougher.
Another physiological phenomenon that can occur when you’re running a marathon above the ideal marathon temperature is cardiac drift.
Cardiac drift is the gradual upward creeping of the heart rate during endurance exercise and is mainly due to dehydration.
As blood plasma volume decreases, the stroke volume, or how much blood is pumped per beat, also decreases.
In order to maintain cardiac output, your heart rate has to increase in order to compensate for the relative reduction in stroke volume.
Even when marathon runners do a good job staying on top of hydration needs, it’s typical to see some amount of cardiac drift over the duration of a marathon.
The extent to which this occurs is also dependent on the environmental conditions, with heat and humidity exacerbating the relative increase in heart rate.
Though cardiac drift occurs to some degree during a marathon or long run, the hotter and more humid it is, the more significant the increase in heart rate.
With cardiac drift, although a marathon runner might complete the race at a fairly even pace, the average heart rate during a marathon will likely still gradually creep up throughout the duration of the race.
A long run or marathon run when it’s above the “optimal running temperature and humidity” will result in a much higher marathon heart rate.
The heart rate is often somewhat high on the starting line due to the circulating catecholamines, such as epinephrine (adrenaline), anxiety, and excitement leading up to the starting gun firing, but as soon as the race is underway, the runner will settle into a comfortable pace.
Let’s say that the runner is running a marathon at a pace that initially correlates to 80% of their maximum heart rate.
In our theoretical example, we will describe the pace as 8:30/mile, and if the max heart rate is 190 bpm, 80% correlates to a heart rate of 152 bpm.
In our scenario, the marathon runner is well-trained and prepared for the race and plans to run even splits.
Thus, if the race unfolds according to plan, he or she will run the entire 26.2 miles at a consistent 8:30 pace.
However, even though this may initially correlate to a heart rate of 152 bpm, or 80% of the runner’s maximum heart rate, this marathon heart rate will slowly increase over the duration of the race due to cardiac drift.
The reason why this matters is that your heart rate in the first half of the marathon will likely be slower than in the second half of the race.
This can happen even if your pace and/or perceived intensity level do not change. When you are running above the ideal marathon temperature, cardiac drift will cause your heart rate to rise, which can increase your rate of perceived exertion and decrease your efficiency.
Research demonstrates that runners who average 5:45 min/mile pace or faster slow down about 1 second per mile for each 1° C (1.8° F) increase in temperature above 15° C (59° F), whereas runners who average 7:25-10:00 min/mile pace slow down 4-4.5 seconds per mile with this same temperature increase.
Although we can’t do much to control the weather on race day or even when you have a long run, trying to stay well hydrated can help minimize the effects of cardiac drift because your blood plasma level will stay as close to normal as possible.
Additionally, choosing shady courses and running in the early morning or evening when you are doing your own training can help you optimize the running weather for performance.
For our complete guide on how to stay well-hydrated for runners, click here!
