A heat wave is a period of intensely hot weather that can pose serious risks. These events signify a notable departure from typical seasonal temperatures. Understanding this phenomenon is increasingly important as heat waves become more frequent and impactful globally.
Defining a Heat Wave
A heat wave is a prolonged period of abnormally hot weather, often with high humidity, where temperatures exceed the usual averages for a region and time of year. While there isn’t one universal definition, a common criterion involves temperatures remaining unusually high for at least two consecutive days. For instance, the World Meteorological Organization (WMO) suggests a heat wave can be a period where the daily maximum temperature surpasses the normal maximum by 9 degrees Fahrenheit (5 degrees Celsius) for more than five consecutive days.
What Causes Heat Waves
Heat waves primarily arise from persistent high-pressure systems in the atmosphere. These systems cause air to sink and compress, leading to warming and drying. This sinking air acts like a cap, trapping warm air near the ground and preventing it from rising and cooling, often resulting in clear skies that allow greater solar radiation to heat the surface. The slow movement of these systems means they can remain over an area for days or weeks, intensifying the heat.
Global climate change also plays a significant role in the increasing frequency, intensity, and duration of heat waves. Rising greenhouse gas emissions from human activities, such as burning fossil fuels, trap more heat in the Earth’s atmosphere, leading to planetary warming. This warmer baseline means that when high-pressure systems occur, heat waves are more severe and prolonged. Climate change can also alter atmospheric circulation patterns, potentially leading to more persistent high-pressure systems that favor heat wave formation. Urban areas can experience an amplified effect due to the urban heat island phenomenon, where concrete and asphalt absorb and retain more heat than surrounding rural areas.
How Heat Waves Affect Us
Heat waves have significant consequences, particularly for public health. Prolonged exposure to extreme heat can lead to conditions like heat exhaustion, heatstroke, and dehydration. It can also worsen existing chronic health conditions such as cardiovascular disease, respiratory issues, and kidney disease. Older adults, young children, pregnant women, and outdoor workers are especially vulnerable. Studies have shown a significant increase in hospitalizations for cardiovascular and respiratory issues during heat waves, with one study indicating a 7% increase on peak heatwave days.
Beyond human health, heat waves strain societal infrastructure and the natural environment. Power grids can become overloaded due to increased demand for air conditioning, leading to widespread electricity outages. Infrastructure like pavement and railway tracks can buckle and warp under extreme temperatures. Agriculture also suffers, with potential for crop damage and reduced yields, leading to economic losses. Dry conditions exacerbated by heat waves increase the risk and severity of wildfires, which worsen air quality and pose additional health risks from smoke inhalation.
Safety Measures During a Heat Wave
During a heat wave, take steps to protect yourself and others from extreme temperatures. Stay hydrated by consistently drinking plenty of water, even if you do not feel thirsty. Avoid alcohol and caffeinated beverages, which contribute to dehydration.
Seek air-conditioned environments like malls, libraries, or designated cooling centers. If air conditioning is unavailable, fans can help if the indoor temperature is below approximately 90°F (32°C); above this, fans can increase body temperature.
Limit strenuous outdoor activities, especially during the hottest parts of the day, typically between 10 a.m. and 4 p.m. If you must be outdoors, seek shade, wear lightweight, loose-fitting, light-colored clothing, and consider a wide-brimmed hat and sunglasses.
Take cool showers or baths and use a damp cloth to cool your skin. Recognize the signs of heat-related illnesses like heat exhaustion (heavy sweating, weakness, dizziness) and heatstroke (confusion, dry skin, rapid pulse). Seek immediate medical attention if heatstroke is suspected.
Check on vulnerable neighbors, friends, and family members, particularly older adults and those with chronic health conditions, to help ensure their safety.