We found an article where they studied the effects of weather conditions on male runners in the Boston Marathon from 1897 to 2018 and thought that its results could be interesting to share, as they represent the data from more than 200 thousand athletes in the world´s oldest annual marathon.
It is clear that environmental conditions affect running performance, with temperature, humidity and wind affecting the body thermoregulatory capacity, and consequently the ability of heat dissipation.
A temperature higher than 35°C and/or humidity higher than 60% will affect detrimentally marathon performance independently of previous heat acclimation or nutrition of the athlete, while affecting also the percentage of finishers.
Best performances for elite finishers (top 100) were in conditions of 8°C and 100% cloud cover. When average temperature increased by 1°C finishing time worsened by almost 2 minutes for all finishers, and around 38 seconds for the top 100 finishers.
The wet-bulb globe temperature, or WBGT, is an index of apparent temperature that takes into account temperature, humidity, wind speed and sunlight radiation. Using this WBGT index the best performance for the top 100 finishers was in the range 0-6°C, and 7-10°C for all finishers. When increasing, it also had a negative effect on performances in all finishers.
As for the wind, it affected negatively normal runners, although benefited the top 100. For them the best results were obtained with speeds of 16-17km/h, which probably helped to refresh the body. The best wind came from West direction. Some rain precipitation was also good for performance, working probably as an extra cooling agent.
The key factor affecting performance in the Boston marathon was undoubtedly the temperature, affecting especially to the slower runners, probably because of a less efficient thermoregulation and a heavier body mass. Additionally, exercise in heat conditions increases glycogen use, lactate production, fatigue and dehydration, which would also affect blood flow to skeletal muscles.
Although not included in the previous study, heat effects are smaller in women, more effective in dissipating the heat because of their larger surface area in relation to their body mass.
The Boston marathon´s results cam probably be extrapolated to other marathons, so don´t blame yourself on your time if weather conditions are difficult. And a note for race organizers to pay attention to dates and starting times of races.
The Role of Environmental Conditions on Marathon Running Performance in Men Competing in Boston Marathon from 1897 to 2018.
Nikolaidis PT, Di Gangi S, Chtourou H, Rüst CA, Rosemann T, Knechtle B
Int J Environ Res Public Health. 2019 Feb 20; 16(4): 614.
Effects of weather on the performance of marathon runners.
Int J Biometeorol. 2010 May; 54(3):297-306.