How Weather Affects Marathon Performance: From the Science to Practical Strategies

The relationship between weather and marathon performance

In a marathon, weather conditions such as temperature, humidity, wind, and rain have a large impact on a runner’s performance. A favorable racing climate is usually around 5-10°C, with moderate wind and no strong sun or rain. Under these conditions, core body temperature is easier to keep stable, the cardiovascular system is under lighter strain, and muscles can work at their best efficiency.

A large body of research confirms that air temperature is the leading environmental factor in marathon performance. The data show that the most favorable temperature for a marathon is roughly 5-10°C, and when the temperature is higher than this range, finishing times gradually slow. For example, one statistical analysis stratified races by the wet-bulb globe temperature (WBGT, an index that combines air temperature and humidity) on race day and found that as WBGT rose from 5°C to 25°C, the times of both men and women declined in a linear fashion. In the coolest group (WBGT 5-10°C), top male runners were on average only 1.7% slower than the course record, but in the hottest group (WBGT 20-25°C) they were 4.5% slower, while the times of top female runners increased from 3.2% to 5.4%.

Although the degree of decline in the heat differed slightly between top male and female runners (the difference in the women’s group did not reach statistical significance, possibly because of larger sample variability), the overall trend was consistent: heat clearly weakens marathon performance. In addition, mid-to-back-pack runners are more affected by heat; the further back a runner places (weaker in ability or slower in pace), the greater the proportion by which they slow in the heat, likely because slower runners are exposed to high temperatures on the course for longer, leading to greater energy expenditure.

By comparison, cold has a less pronounced effect on times than heat, but it can still bring other problems such as muscle stiffness and a risk of hypothermia. It is generally thought that temperatures between a few degrees above freezing and 10°C are relatively favorable for performance, and with appropriate warmth the negative effects of the cold can be reduced. Humidity and rain are more complex factors: moderate rain may have a cooling effect that makes it harder for runners to overheat. In the statistical data from the Stockholm Marathon over 1980-2008, rain on race day was in fact associated with better times for male runners (linked to faster finishing), but the researchers noted that this is mainly because temperatures are usually lower when it rains, rather than the rain itself directly improving performance.

Similarly, when relative humidity is higher, the data show that finishing times are slightly faster, but this is mainly because high humidity is usually accompanied by cooler temperatures. In other words, air temperature is the dominant factor in marathon performance. Within a favorable temperature range, moderate cloud cover (shade) and a light tailwind also help performance. For example, the ideal weather for the Boston Marathon is considered to be 7-10°C, overcast and slightly damp, with a light southerly tailwind. Extreme conditions (heat, heavy rain, or strong wind) clearly lower runners’ performance and can even threaten finishing rates. Research shows that in hot weather the marathon did-not-finish rate rises noticeably, and an analysis of Berlin Marathon data likewise found that heavy rain slows runners across all age groups, with older runners affected especially.

In addition, male runners show declines in performance and dehydration-related distress more often than women in hot and humid conditions; women appear to tolerate heat stress better. This may be related to women having a larger body surface area relative to body weight and therefore more efficient heat dissipation, as well as running at a slower pace.

Boston and Berlin as examples: how does weather affect them differently?

1. The Boston Marathon: the challenge of extreme, variable weather

The Boston Marathon is held in mid-April each year, when the local climate is unstable and has historically seen extremes of intense heat, high wind, heavy rain, and even snow. For example:

• 2012: temperatures spiked to 32°C, causing large numbers of runners to suffer heat illness, and the organizers even allowed runners to defer their entry to the following year.
• 2018: race-day temperatures were only 3°C, accompanied by heavy rain and a headwind, which caused times to fall sharply; most runners underperformed, and some even experienced hypothermia.

These extreme weather challenges test runners’ fitness, gear choices, and mental state, making the Boston Marathon one of the most unpredictable races in the world.

2. The Berlin Marathon: the weather advantage of the world’s fastest course

The Berlin Marathon is usually held in late September, in Germany’s early autumn, when the climate is relatively stable, with average race-day temperatures around 9-15°C and moderate humidity, well suited to fast times. Statistics show that over the past 45 editions of the Berlin Marathon, more than half of race days were clear or partly cloudy, with only a few years seeing sustained rain.

The flat Berlin course and stable weather have made it the birthplace of world records. Almost all modern marathon world records have been set in Berlin, which is closely tied to the local climate.

Coping techniques for different weather conditions

1. Hot conditions: how to avoid heat illness and overheating?

• Training adaptation: do heat-acclimation running beforehand so the body adapts to hot environments.
• Race strategy: ease your pace appropriately, and avoid going out too fast in the first half and collapsing in the second.
• Hydration and electrolytes: take in fluids every 15-20 minutes, paired with sodium-containing drinks to help prevent hyponatremia.
• Gear choices: wear light-colored, breathable, quick-drying clothing, wear a hat for shade, and apply sunscreen.
• Cooling methods: use the sponges and ice at water stations to cool down, pouring water over large blood vessels at the neck and wrists.

2. Cold conditions: how to prevent hypothermia?

• Warm-up: move the body thoroughly before the start to warm the muscles.
• Layered clothing: a moisture-wicking base layer, an insulating mid layer, and a wind- and waterproof outer jacket.
• Protect the extremities: wear gloves, a hat, and a neck gaiter to prevent heat loss.
• Fuel: the body burns more energy in the cold, so take in energy gels and warm drinks at appropriate times.
• Warm up quickly after the race: change into dry clothes immediately after finishing to prevent a sharp drop in body temperature.

3. Rainy conditions: how to reduce the impact?

• Wear water-repellent gear: a light waterproof jacket can reduce rain penetration.
• Shoe and sock choices: avoid cotton socks, choose quick-drying running socks, and apply anti-chafing balm at the toes and heels to prevent blisters.
• Watch for slippery surfaces: slow down on sharp turns and avoid stepping into puddles.
• Protect your eyes: wear a running cap with a longer brim to keep rain from affecting your vision.
• Adjust your mindset: accept the uncertainty of racing in the rain, and focus on holding a steady pace and finishing.

Does rain affect marathon times?

The effect of rain on a marathon depends on the intensity of the rain and the accompanying temperature. Research has found:

• Light rain + cool temperatures (10-15°C): a limited effect, and may even help reduce the risk of overheating.
• Heavy rain + strong wind + cold (below 5°C): a serious impact on times, potentially causing muscle stiffness, increased energy expenditure, and a risk of hypothermia.
• Berlin Marathon data show that some world records were set in overcast, rainy weather, indicating that moderate rain is not necessarily an unfavorable factor.
• The 2018 Boston Marathon shows that heavy rain combined with cold temperatures did clearly lower runners’ times, and even caused large numbers to drop out.

In summary, the effect of rain varies from person to person: light rain has a limited effect, but cold, heavy rain is a clearly unfavorable condition. Runners should therefore adjust their strategy and gear to the race-day weather to help ensure their best performance.

Whatever the weather on race day, successful marathon runners know how to adapt and adjust their strategy. Understanding the typical climate of the race location and choosing suitable clothing and fueling strategies for the actual conditions are key to maintaining good performance. Finally, keeping a steady mindset and viewing weather changes as a challenge rather than an obstacle lets you perform at your best in any conditions.

References

• Med Sci Sports Exerc. 2007 Mar;39(3):487-93.
• Front Physiol. 2021 May 13;12:654544.
• Front Physiol. 2021 May 28;12:654860.

Further reading

• Runner topic
• Sports injury overview
• PRP prolotherapy
• Rehabilitation exercise prescription
• Pain management