What is a Heat Wave?

Malcolm Tatum

Heat waves are periods of time where the weather is significantly warmer than is usual for the season and usual climate. In spite of differences in opinion of what exactly constitutes this type of weather condition, many locations around the world routinely report experiencing a heat wave at some point during the calendar year. In some places, the heat wave is a common phenomenon that takes place during the summer months, although a weather condition of this type of not limited to a particular season.

Drink plenty of water to avoid dehydration during a heat wave.
Drink plenty of water to avoid dehydration during a heat wave.

While qualifying a hot weather condition as a heat wave varies from one location to another, there are a few basic facts on heat waves that seem to apply just about everywhere. First, the weather is noticeably warmer than is considered normal for the time of year and the climate. Second, the unusual weather continues for a period of time considered sufficient to be considered a specific phase. Last, the weather is likely to bring about some type of increased risk to people, animals, and may place additional strain on power supplies.

There are many dangers during a heat wave that can lead to heat exhaustion or heat stroke.
There are many dangers during a heat wave that can lead to heat exhaustion or heat stroke.

In general, the main cause of heat waves has to do with the positioning of the jet stream in an area where a significant amount of high pressure is present in the atmosphere. The air found on one side of the jet stream is likely to be much warmer than on the opposing side. At the same time, if the higher pressure in the region is characterized by almost no cloud cover or precipitation, the air and top level of ground are heated to temperatures above the normal range for that time of year. As long as the cloud cover remains thin and there is not sufficient precipitation to cool the air and ground, a heat wave is likely to develop.

Different places around the world define a heat wave as lasting for specific periods of time. In some locations, the weather conditions must persist for a minimum of three calendar days before the phenomenon is classified as a wave. In other areas, a period as short as twenty-four consecutive hours of unusually warm weather is sufficient.

There are dangers related to the occurrence of a heat wave. Dehydration may also occur if care is not taken to drink sufficient quantities of liquid during a prolonged wave of heat. The condition can lead to the incidence of heat exhaustion or heat stroke. Additional stress on power supplies as people attempt to remain comfortable with air conditioning can lead to power failures at different points along a power grid. During a heat wave, it is important to check on elderly relatives and neighbors, provide shade and plenty of water for pets, and in general find ways to keep the body properly hydrated.

What is considered a heat wave in one location during a given season may not be considered to be an unusual phenomenon in another part of the world. For example, high temperatures with excessive humidity during the month of July may be considered unusual in the New England area of the United States, but would be normal in the Deep South during the same time frame.

Spritzing with water is a way to stay cool during a heat wave.
Spritzing with water is a way to stay cool during a heat wave.

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Discussion Comments


@ aplenty- I just graduated with a degree in economics, and I have to agree with glasshouse. Most non-political agencies within the government are preparing for the consequences of a warmer world, but until policy changes we will be left behind. For example, the Pentagon has stated in their last quadrennieal review that “While climate change alone does not cause conflict, it may act as an accelerant of instability or conflict, placing a burden to respond on civilian institutions and militaries around the world”. There will be tradeoffs, but the sooner we begin to attack the root causes of climate change, the better we insulate ourselves, and our economy, from the consequences.

The biggest hurdle is to change policy. Politicians by nature only look for short-term solutions because they are only out to secure their next political appointment. This means that they would rather take the millions of dollars and support from multinationals that spend more money on lobbying than they do in taxes, than change policy in favor of their taxpaying "constituents".


@ aplenty- I don't think most rational people believe the world will come to an end. Humans are not that special. Nevertheless, it is time to make a decision about how we want our economy to look moving forward, and what types of sacrifices we are willing to make. Are we willing to make sacrifices to change the current economic model of our nation, which currently is unstable, or are we willing to sacrifice the lives of our soldiers, personal liberties, and future economic security so that we can have a chance at a short term recovery? The point being made about global warming is it is no longer an environmental problem. It has become an economic and social problem, and not just for us.

If you lift the veil over your eyes, you would see that the rest of the world gets it and they are moving on. China says that they don't want to agree to cut emissions, but they have internal policies that are shifting their economy to a sustainable one, same with India, Brazil, all of Europe, and the likes. We are at risk of being left behind, and slipping further into the ranks of just another country.


@ ValleyFiah- I am honestly sick of hearing about all of this global warming stuff. It’s not like the world is going to come to an end. It's getting a little warmer...what's the big deal. I mean honestly, the temperature goes up a few degrees, but that should not mean we put the brakes on our entire economy and pour all of our resources into environmental measures that are just as unproven as the science of global warming. I respect your opinion, but I also ask what you propose should be done. Should we invest massive amounts of money into renewable energy when we have plenty of energy within our borders? Should we start taxing our emissions so more companies move overseas? I just don't see the logic in changing our system when the rest of the world does not want to do the same.


While the jet stream may be the weather related cause of a heat wave, the frequency and severity of heat waves are due to many more factors than atmospheric pressure. Believe it or not, we are in the midst of a global heat wave that has produced one of the hottest years on record. According to the NOAA, the first half of this year has produced higher global surface and oceanic temperatures than any other year that records have been kept. There has been an increase in temperature of 1.22 degrees Fahrenheit over years past. It is not necessarily a definitive indicator that global warming is human caused, but it is an indicator that the earth is going through a period of warming.

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