How Weather Affects Your Marathon: Why Environmental Factors Can Make or Break Your Race Day
- Luke Bialobzyski, CSEP-CPT
- May 5
- 7 min read
The Marathon Weather Problem
You've put in hundreds of training miles. You've dialed in your nutrition. Your taper was perfect. But then race day arrives with an unexpected heat wave, and suddenly your goal time feels impossibly out of reach.
This scenario plays out thousands of times every race season, leaving runners frustrated and questioning where they went wrong. The truth? Sometimes it's not your training or preparation that's the problem—it's the weather.
Recent research has shown just how dramatically environmental conditions can impact marathon times across all ability levels. By understanding these effects, you can make smarter race choices and adjust your expectations and strategy when Mother Nature throws you a curveball.
Ready to take your marathon training to the next level? Our personalized coaching programs account for environmental factors in your training plan and race strategy. Apply for 1-on-1 coaching today and stop letting weather sabotage your marathon goals!
Temperature: Your Biggest Performance Killer
When it comes to marathon performance, temperature is public enemy #1. Multiple studies have confirmed that as temperatures rise above the ideal range, performance steadily declines.
Research from the Berlin Marathon examining over 668,000 runners found a clear negative correlation between rising temperatures and running speed (Weiss et al., 2024). Another study looking at six major marathons and nearly 1.8 million performances discovered that air temperature and performance were significantly linked (El Helou et al., 2012).
What does this mean in practical terms? When temperatures rise:
Your body diverts blood away from working muscles to cool your skin
Your heart works harder to maintain both cooling and muscle function
Your perceived effort increases even though you're running slower
Your risk of heat-related illness climbs dramatically
For every 5°C (9°F) increase above optimal temperature, expect your marathon time to slow by roughly 1-3% depending on your pace—that's 2-9 minutes for a 3-hour marathoner!
Humidity: When Sweat Won't Save You
While temperature gets most of the attention, humidity plays a crucial supporting role in sabotaging your marathon.
High humidity prevents sweat from evaporating efficiently, which is your body's primary cooling mechanism during a marathon. When both temperature and humidity are high, you're facing a double threat.
Interestingly, research by Vihma (2010) found that relative humidity (the percentage of maximum water vapor the air can hold) often showed a negative correlation with marathon times—suggesting better performance in higher humidity. However, this is misleading because cooler days tend to have higher relative humidity, and it's really the cooler temperature improving performance.
What really matters is the actual water content in the air (specific humidity). When this is high, your sweat doesn't evaporate well, and your body temperature climbs even faster.
Sunshine: More Than Just a Tan Risk
Direct sunlight can add significant heat stress beyond what air temperature alone indicates. Weiss et al. (2024) found that average pace showed positive correlations with minutes of sunshine for both men and women—meaning more sunshine was associated with slower performances.
Solar radiation directly adds to your body's heat load. While your internal temperature might be 98.6°F (37°C), the surface of your skin exposed to direct sunlight can reach much higher temperatures, making cooling more difficult.
This is particularly impactful for slower runners who spend more time on the course. If your marathon starts at 7 AM but you're running for 5+ hours, you'll experience the hottest, sunniest part of the day when solar radiation is at its peak.
Wind: Friend or Foe?
Wind's relationship with marathon performance is complicated. In theory, wind can help cool you down on hot days by enhancing sweat evaporation and convective cooling.
However, running into a headwind increases your energy expenditure significantly. Physics tells us that the disadvantage of running into a headwind actually outweighs the advantage gained from an equivalent tailwind. This is because air resistance increases with the cube of your relative speed.
On race day, wind direction and strength can vary throughout the course, sometimes helping and sometimes hindering. Research generally shows minimal overall impact of wind on marathon times compared to temperature and humidity.
Rain: Blessing or Curse?
Light rain during hot conditions can be a blessing, providing external cooling that helps manage body temperature. However, heavy rain creates its own challenges:
Wet, heavy clothing that increases energy expenditure
Potential for blisters and chafing
Slippery surfaces that may force a more cautious pace
Research by Vihma (2010) found that light rain during marathons was often associated with better finishing times, but this effect disappeared when controlling for temperature—rainy days tend to be cooler.
Rain's ultimate impact on your performance largely depends on the temperature and your preparation (appropriate clothing, anti-chafing strategies, etc.).
Who Suffers Most? It Might Be You
One of the most consistent findings across studies is that environmental conditions affect different runners to varying degrees. Bad news if you're not an elite: slower runners typically suffer more in challenging weather.
Vihma (2010) found that increasing air temperature from 10°C to 25°C (50°F to 77°F) added about 5 minutes to elite runners' times but a whopping 23 minutes for 4-hour marathoners.
Several factors explain why average runners struggle more in tough conditions:
Recreational runners often have larger body mass, increasing heat production
Elite runners have more efficient cardiovascular systems that better manage blood flow for both cooling and muscle function
Slower runners spend more time on the course, experiencing more heat exposure
Mid-pack runners often run in crowds, which reduces cooling from air flow and radiation
If you're targeting a 3:30+ marathon finish, weather impacts you much more than your speedy friends at the front of the pack.
Men vs. Women: Who Handles Heat Better?
Interesting gender differences emerge when looking at environmental impacts on marathon performance.
Research consistently shows that women tend to be less affected by temperature increases than men. The correlation between temperature and running speed is stronger among male runners (Weiss et al., 2024).
This advantage likely stems from physiological differences:
Women typically have higher surface area-to-mass ratios
Women generally run at slower absolute speeds, producing less metabolic heat
Women may have different thermoregulatory responses
These differences give women a potential advantage in heat dissipation during marathon running, explaining their relative resilience to temperature increases compared to men.
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Your Perfect Race Day Weather
Based on the research, the ideal marathon conditions are:
Temperature: 10-15°C (50-59°F)
Low humidity
Moderate cloud cover
Light wind
No precipitation or very light precipitation
These conditions optimize your body's ability to balance heat production and dissipation while running at marathon effort.
El Helou et al. (2012) concluded that air temperature has the most significant influence on marathon performance compared to all other environmental factors. If you're targeting a PR or Boston qualifying time, prioritize races known for favorable temperatures in this range.
When to Quit: DNF Considerations
Beyond performance impacts, environmental conditions significantly affect safety and did-not-finish (DNF) rates.
Research shows that both the percentage of non-finishers and medical incidents increase dramatically as temperatures rise. Vihma (2010) found that non-finisher rates were significantly affected by air temperature and humidity.
While DNFing is always a difficult decision, it's important to recognize when continuing might pose serious health risks. Warning signs that the weather might be too extreme include:
Dizziness or confusion
Nausea that prevents fluid intake
Muscle cramping that doesn't respond to electrolytes
Chills despite hot conditions
Stopping sweating in hot conditions
Heart rate that won't decrease even when slowing down
No medal is worth serious health consequences. Trust your body's signals in extreme conditions.
Smart Weather Strategies for Runners
While you can't control the weather, you can control how you prepare for and respond to it:
Before Race Day:
Choose races known for favorable conditions in your target time range
Train in similar conditions when possible to promote acclimatization
Practice your hydration and cooling strategies in training
Have a "weather plan" with adjusted goal times for different conditions
Race Day Adjustments:
Revise your goal time based on actual conditions (use online calculators or the 1-3% rule)
Start conservatively in challenging conditions
Increase fluid and electrolyte intake in hot or humid conditions
Use cooling strategies like pouring water over your head and neck
Adjust your pacing strategy—hot conditions often require more even pacing or even a slight negative split
Post-Race Learning:
Document the conditions and your performance
Note what worked and what didn't with your coping strategies
Use this information to better prepare for similar conditions in the future
Conclusion
Environmental factors, particularly temperature, have a profound impact on marathon performance at all levels. While elite runners may lose a few minutes in challenging conditions, average marathoners can see their times slow by 20+ minutes when the mercury rises.
Understanding these effects allows you to make smarter race choices, set realistic expectations, and develop effective strategies for different conditions. Don't beat yourself up over a disappointing performance in tough weather—instead, use that experience to become a more adaptable, resilient runner.
The next time you're choosing a marathon, consider the typical weather patterns along with the course profile and logistics. And remember, even in perfect conditions, marathon success comes from proper training, smart pacing, and mental toughness.
Weather may be unpredictable, but your preparation doesn't have to be.
Ready to take your marathon training to the next level? Our personalized coaching programs account for environmental factors in your training plan and race strategy. Apply for 1-on-1 coaching today and stop letting weather sabotage your marathon goals!
References
El Helou, N., Tafflet, M., Berthelot, G., Tolaini, J., Marc, A., Guillaume, M., Hausswirth, C., & Toussaint, J. F. (2012). Impact of environmental parameters on marathon running performance. PLoS ONE, 7(5), e37407. https://doi.org/10.1371/journal.pone.0037407
Vihma, T. (2010). Effects of weather on the performance of marathon runners. International Journal of Biometeorology, 54(3), 297-306. https://doi.org/10.1007/s00484-009-0280-x
Weiss, K., Valero, D., Villiger, E., Scheer, V., Thuany, M., Aidar, F. J., de Souza, R. F., Cuk, I., Nikolaidis, P. T., Rosemann, T., & Knechtle, B. (2024). Associations between environmental factors and running performance: An observational study of the Berlin Marathon. PLoS ONE, 19(10), e0312097. https://doi.org/10.1371/journal.pone.0312097
Roberts, W. O. (2000). A 12-yr profile of medical injury and illness for the Twin Cities Marathon. Medicine & Science in Sports & Exercise, 32(9), 1549-1555. https://doi.org/10.1097/00005768-200009000-00004
Ely, M. R., Cheuvront, S. N., Roberts, W. O., & Montain, S. J. (2007). Impact of weather on marathon-running performance. Medicine & Science in Sports & Exercise, 39(3), 487-493. https://doi.org/10.1249/mss.0b013e31802d3aba