As 2024 ushers in an intense summer heat wave across many regions, anyone who spends time outdoors—from dedicated runners and cyclists to outdoor workers and active kids—faces real health risks. When temperatures soar and humidity climbs, the threat of heat-related illnesses becomes more than just uncomfortable; it can be dangerous.
Susan Yeargin, an expert in heat-related illnesses and Associate Professor of Athletic Training at the University of South Carolina, shares critical insights on how heat affects the body and offers practical advice to protect yourself and vulnerable loved ones during these extreme conditions.
Why Heat Poses a Threat to Outdoor Activities
The risk from heat depends heavily on when you’re outside. Early morning or evening exercisers benefit from cooler air and less direct sunlight, which significantly reduces heat exposure. Conversely, running, walking, or cycling during the midmorning or midday hours—typically between 10 a.m. and 6 p.m.—means battling the highest air temperatures and intense solar radiation.
Adding to this challenge, heat radiates not just from the sun but also from the warmed ground beneath your feet or wheels—think hot asphalt or sunbaked grass. Humidity compounds the problem by impeding your body’s ability to cool itself through sweating.
Furthermore, physical activity generates internal heat. The more intense the effort—whether sprinting, cycling uphill, or even doing yard work—the greater the heat your body produces. Outdoor workers, such as those on farms or construction sites, may face prolonged exposure with limited opportunities for breaks, putting them at elevated risk.
Can Our Bodies Adapt to Heat?
Fortunately, the human body is capable of remarkable adaptation. Typically, it takes about two weeks to acclimate to higher temperatures. During this time, your sweat response improves, helping your body dissipate heat more efficiently. Your plasma volume (the fluid component of blood) increases, easing the heart’s workload and stabilizing internal temperatures. Your body also becomes better at retaining salt, which helps maintain hydration.
But acclimatization is not a cure-all. Being used to 80°F weather doesn’t mean you’re ready to safely handle sudden spikes to 95°F or higher, especially when combined with high humidity. Early-season heat waves are particularly dangerous because the body hasn’t had time to adjust.
Who’s Most Vulnerable?
Older adults and young children are especially susceptible to heat-related illnesses. As people age, their cardiovascular systems become less efficient, and sweat production decreases, undermining the body’s ability to cool down. Thirst sensation also diminishes, raising dehydration risks. Additionally, older adults may be less likely to seek cooler environments when they feel unwell.
Children take longer to acclimatize and rely more on skin heat loss than sweating, often showing flushed skin as a warning sign. Fortunately, kids tend to communicate discomfort, so caregivers should be attentive to their cues and encourage breaks and hydration.
Six Practical Tips to Stay Safe in Extreme Heat
- Time Your Activities Wisely
Aim to exercise or work outdoors early in the morning or late in the evening when temperatures are cooler. Avoid strenuous activity during the peak heat hours. If you must be outside, seek shaded areas to reduce direct sun exposure. - Stay Hydrated—Don’t Ignore Thirst
Your body signals dehydration through thirst. Drinking fluids regularly helps maintain blood volume, easing cardiovascular strain and improving heat tolerance. Since muscles and the brain are largely water, hydration also supports performance and cognition. - Listen to Your Body
If you feel dizzy, excessively hot, or fatigued, slow down or rest. Your body will give you signs when heat stress is mounting—heeding these signals can prevent serious illness. - Dress Smart
Wear lightweight, loose-fitting, light-colored clothing that reflects sunlight and allows sweat to evaporate. Avoid heavy or dark fabrics that trap heat. For those who wear helmets or sports gear, recognize these items can trap heat and take extra precautions to cool down. - Ensure Quality Sleep
Heat exposure affects more than your daytime comfort—it can impair your sleep quality, increasing heat illness risk the next day. Air-conditioned or well-ventilated rooms can help you rest and recover. - Protect Vulnerable Individuals
Keep an eye on older adults and children, ensuring they stay hydrated and cool. Encourage breaks and access to air-conditioned or shaded environments.
Beyond Personal Precautions: The Bigger Picture
While individual strategies are essential, broader public health efforts play a crucial role in combating heat risks. Employers should provide cooling breaks and shaded rest areas for outdoor workers. Communities can promote access to cooling centers and educate residents about heat safety.
Final Thoughts
Extreme heat is more than a nuisance—it’s a genuine health threat, especially as climate change drives more frequent and intense heat waves. By understanding how heat impacts the body and taking proactive steps, you can safely enjoy outdoor activities even in challenging weather.
As Susan Yeargin emphasizes, staying informed, planning wisely, and listening to your body are your best defenses against heat-related illnesses this summer.
