Heat wave information

Direct Energy, December 12, 2023

5 minute read

Heat wave information

Direct Energy, December 12, 2023

5 minute read

What is a heat wave?

A heat wave is an extremely dangerous weather condition where temperatures soar well above 90° F. This high heat combines with high levels of humidity and creates a heat bubble over a certain area for an extended period of time.

How do heat waves form?

Heat waves form when high-pressure air settles high in the air and causes hot air to sink down. The hot air sinking creates a bubble that acts like a seal and traps heat near the ground. This seal keeps out convection currents that eventually form rain clouds, both of which would help the area affected cool off. Instead, the result is a heat wave that has both high heat and high humidity near the ground. These heat waves can last from days to weeks.

What causes a heat wave?

Heat waves are caused by a strong high pressure settling in at 10,000-25,000 ft. and not moving. This causes warm air to sink. The result is a dome of hot air that traps the heat near the ground and prevents cooling convection currents from forming clouds.

Heat waves cause earthquakes.
Heat waves are due to global warming.


Heat waves only occur in August.



Heat waves cause power outages.


Heat waves can cause drought and wildfires, not earthquakes.
Global warming may be increasing the number of heat waves but it is not the sole cause of heat waves.
Heat waves take place in the summer months, which change depending upon where you are in the world.
Heat waves themselves don't cause the power outage; instead the increased electricity consumption combined with the high temperatures can lead to power outages.

How hot can a heat wave get?

The temperature of a heat wave is well over 90° F with high humidity, making it feel a great deal hotter. Weather forecasters use a heat index to determine how much hotter the effect of the humidity is making the day feel. For example, if it is 84.5° F with humidity levels of 84%, the day feels more like 98° F. 

Where do heat waves occur?

Heat waves are not just confined to the areas we usually think of as hot. Heat waves can occur anywhere high-pressure air settles. This still creates an environment that can form a heat dome. 

How do I know when to expect a heat wave?

The best way to know when to expect a heat wave is by tuning to the national weather service and understanding what their issues and warnings mean.

  • Excessive Heat Outlooks – Issued when there is potential for excessive heat event in the next week.
  • Heat Advisory – Issued within 12 hours of when maximum heat index temperatures could exceed 100° F or higher for at least 2 days and nighttime air doesn't don't drop below 75° F.
  • Heat Watches – Issued when conditions are favorable for excessive heat in the next 24-72 hours.
  • Excessive Heat Warning – Issued within 12 hours of the onset of extremely dangerous heat conditions where the maximum heat index temperature is expected to be 105° F or higher for at least 2 days and nighttime air doesn't drop below 75° F.

What is a heat advisory?

A heat advisory is a warning issued when the maximum heat index temperatures could exceed 100° F or higher for at least two days without the evening air dropping below 75° F.

Is a heat wave a natural disaster?

While heat waves may not have the excessive winds or rain that you think of when considering natural disasters, they are in fact a natural disaster. 

How do heat waves affect the environment?

Heat waves affect the environment through both high temperatures and low rainfall. These two factors combine to make conditions ideal for droughts and wildfires. The droughts and wildfires caused by heat waves can have huge influences on the surrounding vegetation and wildlife. Plants that need higher levels of water or more shade can die as a result of heat waves. Wildlife struggling to keep cool or find adequate water can also perish, which in turn, can affect the environment and their respective ecosystems.

What are the dangers of a heat wave?

Heat waves can be one of the most threatening weather phenomena. This is due to the fact that heat waves not only have high temperatures but also high levels of humidity. Humidity hinders the body's ability to sweat;  the higher the humidity the hotter the day feels.

Some of the main dangers associated with heat waves are dehydration, heat exhaustion, heatstroke and even death. The effects of heat waves are extremely dangerous for infants and the elderly because both can have difficulty maintaining body temperature. Additionally, those unable to take shelter in a cooled building can be extremely impacted by the dangers of heat waves.

How a heat wave affects humans

  • Temperature – During heat exhaustion, you will be excessively sweating. However, during a heat stroke the high levels of humidity in the air could hinder your body's ability to sweat. 
  • Skin – During heat exhaustion, your skin will feel cool and clammy. However, once your body temperature rises above 104°F, your skin will feel hot and dry. putting you in serious danger of heat stroke.
  • Head – The high temperatures during a heat wave can cause the body to lose too much water, leading to dehydration. If you're suffering from heat exhaustion, you will feel faint and dizzy. If you're suffering heat stroke, you will have a severe headache.
  • Stomach – Heat exhaustion occurs when your body is no longer able to cool itself, which can cause nausea or vomiting..
  • Legs – You may experience muscle cramps, another symptom of heat exhaustion.

How to keep yourself and your pets cool during a heat wave

  • Stay inside – As much as possible, stay inside air conditioned buildings.
  • Dress light  Wear loose fitting and lightweight clothes.
  • Keep hydrated  Limit the risk of dehydration by consciously consuming enough water.
  • Eat less  You'll feel the effects of heat waves less if you eat lighter meals and avoid feeling full.
  • Find shade  If you have to go outside, seek out shaded areas.
  • Stay smart with energy use  Don't use appliances like ovens, dishwashers and dryers during the day to avoid heating up your house.
  • Bring your pet indoors  Even if they're outside animals, the high temperatures and high humidity could easily cause your pet to overheat.
  • Make sure your pets have plenty of water – This helps keep them from experiencing dehydration and heat stroke.
  • Watch how much your pets eat  Full stomachs can help increase symptoms of dehydration and nausea. Help your pet stay cool by not letting them eat too much.

What do I do during a heat wave if I don’t have air conditioning?

During a heat wave it’s important that you try and keep yourself cool. Without AC this can be tricky, but not impossible. When possible, leave your home to seek out places that do have AC. But in order to keep your home as cool as possible open your windows at night to let in cool air. In the morning, close windows to try and shut out the day's heat for as long as possible. Only open them when it gets too stuffy. You should place fans strategically in your home to create cross breezes.

How do heat waves affect animals?

Animals, just like humans, are affected by the high temperatures and high levels of humidity. But unlike humans, they may not have access to an air-conditioned building. You may see fewer animals out around you – as they will probably seek out shaded areas to try and escape the heat.

How do heat waves affect the economy?

Potentially higher prices  Even short droughts caused by the excessive heat in a heatwave can decrease plant production and result in higher prices in the market.

More energy usage – Keeping cool during a heatwave increases energy consumption due to running air conditioners. 

Can heat waves impact the power grid?

When temperatures rise, increased air conditioning use means more electricity demand, which can put extra stress on the electric grid. High temperatures can also have a physical impact on transmission lines. Working together to conserve electricity, especailly during a heatwave, means a better chance for us to stay cool and comfortable.

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