Posted by Weatherflow ● August, 2022

Staying Safe During a Heat Wave


Extreme heat cautionary sign on side of road

In recent years, a series of record-breaking heat waves around the world has brought heat waves and their hazards into the public consciousness. With the effects of climate change likely to increase the frequency and severity of heat waves over the coming decades, the hazards related to them are expected to worsen. As the environment and human health can be negatively affected by more severe and frequent heat waves, it will be important to know how to stay safe.


Heatwaves are prolonged periods of excessive heat, with temperatures above the average for that region and season. They are typically caused by high-pressure weather events, which move into an area compressing the air and increasing the temperature. High pressure, also called anticyclone events, is caused by air cooling at high altitudes and descending, creating a slow-moving “heat dome,” which can last multiple days, weeks, or months. Periods of high pressure are also characterized by less cloud cover and low winds resulting in further increases in heat. Recent studies have also shown that the urban heat island is a factor in heat waves, with the mass of concrete, asphalt, and lack of green space absorbing heat, making cities up to 9⁰F above surrounding areas.


Since the industrial revolution, climate change caused by increased greenhouse gasses in the atmosphere has caused global average temperatures to increase by 1.8⁰F. Climate change is predicted to further increase the global average temperature by between 3.6-7.2⁰F by 2100. Since the 1960s, global temperatures have risen by 1.3⁰F. During that time, heat wave characteristics in the US have seen similar increases, with the average number of heat waves per year tripling, the average length of individual heatwaves increasing by a day, and the number of cumulative heat wave days and the average temperature of heatwaves increasing. The simple version of how climate change exacerbates heat waves is carbon in the atmosphere traps heat, meaning the more carbon in the atmosphere, the hotter the planet becomes, and as the concentration of carbon in the atmosphere continues to rise, so too will the severity and frequency of heat waves.


While most think of heat waves as prolonged periods of “nice” weather, in reality, heat waves can be deadly and have been responsible for more fatalities in the US than any other extreme weather event over the last 30 years. Although the primary effect on human health of heat waves comes from direct heat exposure causing heat strokes, heat stress, and dehydration, the tertiary results of prolonged bouts of heat in the way of droughts can have worse consequences. A drought can have knock-on effects on the supply of both drinking water and water for agriculture, which can cause food shortages and famines in extreme cases.


Across the last decade, many countries have seen some of their hottest periods of record-breaking heat waves. For example, in the summer of 2022, a European heat wave saw the highest temperature in the United Kingdom at 104.5F. But the effects of this year's heat wave across Europe pales in comparison to some of the hottest, longest, and most deadly heatwaves in history.

  • The hottest heat wave of all time came in July 1913, when a heat wave across California saw the mercury tipping 134F in Death Valley.
  • The most prolonged continuous heatwave came in 1936 in Yuma, Arizona, where they experienced 101 days of constant temperatures above 100F.
  • The most deadly heat wave came across Europe on July 20th and August 20th, 2003. During that time, the death toll reached above 70,000, with temperature highs of over 104F.


With heat waves predicted to worsen in the coming decades, it will be essential to protect yourself and your community against its effects. The methods to prevent heat-related illnesses and injuries may seem common sense, but they could be life-saving. They include drinking plenty of water, staying in air-conditioned rooms, especially during the hottest times of the day, taking cool showers, and scheduling outdoor activities at cooler times of the day. Although these measures apply to everyone, those at the highest risk should be closely monitored. High-risk people include those over 65, under two years old, and those with chronic illnesses.

Staying informed about the conditions where you live can help you stay one step ahead of the heat. The HeatAlert app informs users of current conditions and forecasts specifically for heat, including wet bulb globe temperature. Wet bulb globe temperature (WBGT) uses a combination of temperature, humidity, pressure, solar radiation, and wind speed to indicate estimated heat stress levels for humans and animals in direct sunlight. Monitoring WBGT can help prevent heat-related illness and injury for anyone spending time outdoors. 


Although heat waves may seem more manageable than other forms of extreme weather, they are actually some of the most threatening weather events for human health. As heat waves continue to increase in severity and frequency, protection from potential adverse health effects will be more of a necessity. By following some of the safety precautions in this guide, you will be able to stave off the worst impacts of possible heat waves and keep you and your family safe in even the most severe prolonged heat event.

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