Discover the June Heatwave That Turned the United States Into a Fiery Oven

Written by Patrick Sather
Updated: June 8, 2023
© VladisChern/
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For many people, June represents the start of summer fun, a time to enjoy barbeques, dips in the pool, and trips to the beach. However, some June heatwaves can make enjoying many summer activities almost impossible. Heatwaves are periods of unusually high temperatures and humidity that affect certain climates. While normally short, these periods can sustain for several weeks or even months. Some experts argue the climate change brought about by the releasing of too many greenhouse gases will only serve to make heatwaves hotter, longer, and more frequent. That said, what is the hottest June heatwave to ever hit the United States?

The worst June heatwave on record in the U.S. occurred in 2021. We’ll examine the context of this climate event as well as the impacts it had on people, the economy, and the environment. Additionally, we’ll discuss what can be done to prepare for future heatwaves on a personal and societal level. Get ready to discover the June heatwave that turned the United States into a fiery oven. 

History of Heatwaves in the United States

The United States has experienced numerous record-setting heatwaves
The United States has experienced numerous record-setting heatwaves in its history.


Take a peek back through history, and you’ll quickly see that heatwaves aren’t a new phenomenon. On the contrary, heatwaves appear periodically depending on prevailing climate and weather patterns. At the same time, certain events, such as the rapid global heating that began to occur in the 20th century, have led to an increasing number of powerful, sustained heatwaves worldwide. Let’s take a look at some of the strongest heatwaves in U.S. history. 

The 1896 New York heatwave ranks as one of the worst – and least remembered – natural disasters in U.S. history. Over the course of 10 days in August 1896, temperatures in the city remained above 90 degrees Fahrenheit. The high temperatures – accompanied by high humidity – eventually claimed 1,300 lives. Nearly 40 years later, the 1936 North American heatwave caused immense human and economic suffering across much of the United States. The heatwave was responsible for around 5,000 deaths and destroyed many crops due to high heat and drought. More recently, the 2012 North American heatwave made records as one of the worst in history. The heatwave resulted in around 100 deaths and caused billions of dollars in damage due to drought. 

The 1980 United States heatwave ranks as one of the worst heatwaves in the country’s history. This heatwave began in June due to the formation of a strong high-pressure ridge in the southern and central United States. This ridge prevented the formation of thunderstorms, which led to persistent drought and also caused temperatures to climb well above 90 degrees Fahrenheit for almost 3 months straight. The heatwave claimed at least 1,260 lives but may have indirectly caused the deaths of up to 10,000 people. On top of the human death toll, it also caused approximately $20 billion (over $73 billion in 2023) in agricultural damage. 

The 2021 June Heatwave

The June 2021 heatwave ranks as the warmest June on record in U.S. history. During the month of June, around 15 percent of the contiguous U.S. observed the warmest temperatures on record. Five states on the west coast and three in the northeast set all-time heat records for June. States that set new records included Arizona, California, Idaho, Massachusetts, Nevada, New Hampshire, Rhode Island, and Utah. Meanwhile, the month of June averaged out as the 2nd hottest on record for Connecticut, Maine, Montana, Oregon, Washington, and Wyoming. Overall, the contiguous U.S. June temperature clocked in at 72.6 degrees Fahrenheit, around 4.2 degrees above the average for the 20th century. 2021 beat the previous record set in 2016 by nearly 0.9 degrees Fahrenheit. From January to June, the year 2021 also ranked as the 3rd-warmest on record for the contiguous U.S. 

Portland, Oregon, reached 117 degrees Fahrenheit on June 28, the highest June temperature ever recorded in the city. Similarly, Seattle hit 108 degrees Fahrenheit on June 28, another record high. On the other side of the country, New York City, Boston, and Newark all experienced temperatures in the upper 90s, well above normal. 

The high temperatures in June 2021 were caused by a dome or ridge of hot air centered over the U.S. and Canada. This ridge of high-pressure air effectively blocked cyclones and other winds from passing through, which could have cooled the region. Normally, these barometric ridges can last anywhere from a few days to a few weeks. However, the June 2021 ridges in the northwest and northeast of the U.S. exhibited enormous staying power. This was likely due to the presence of low-pressure regions above and below the high-pressure ridges, effectively trapping the hot air in place. 

How Did People Cope With the 2021 June Heatwave?

Woman protects herself from the hot sun
Heatwaves can prove dangerous if you don’t take the proper precautions.

©Nelson Antoine/

The June 2021 heat wave was an ultra-rate weather event made all the worse by climate change. The record-high temperatures caused numerous deaths, hospitalizations, and other health issues for residents across the United States and Canada. It’s difficult to estimate the exact death toll caused by the heatwave. Analysis reports suggest around 1,400 people died as a result of the heatwave. Around 800 of the deaths attributed to the heatwave occurred in Canada. As for the 400 or so deaths in the United States, most occurred in Oregon (116) and Washington (112). 

The heatwave led to a massive uptick in hospitalizations and 9-1-1 calls related to heatstroke. To combat the heat, people flocked to stores to purchase air conditioning units. This led to an increase in prices and a massive supply shortage. Some people without air conditioning chose to rent hotel rooms with A/C or to travel out of state. Others flocked to rivers, lakes, and pools to cool off. 

Economic Impact of the June 2021 Heatwave

According to the National Oceanic and Atmospheric Administration, the June 2021 heatwave caused around $8.9 billion in damages across the U.S. Much of this loss resulted from the destruction of agricultural crops, damaged infrastructure, and lost business revenue. The heatwave caused sidewalks to crack and buckle, which led to road closures. Similarly, rail lines slowed traffic due to the risk of railroad tracks deforming due to the heat. In Portland, the temperature got so hot that it caused power cables to burst. Numerous businesses chose to shutter their doors rather than subject their employees and clients to the heat. In addition to cafes, grocers, and restaurants, several schools also closed for a few days due to the heat. 

Environmental Impact of the June 2021 Heatwave

Barnacles, oysters, and clams died in their millions during the 2021 June heatwave.

©Malt House Photography/

The June 2021 heatwave impacted wildlife, agriculture, and native habitats across the United States and Canada. Wildfires blazed across much of the west coast of Canada and the United States. These fires burned hundreds of thousands of acres of dry forests and developed land. The high temperatures also accelerated glacial melt in mountain regions across the most-affected regions. This additional melting also increased glacial runoff, which led to flash flooding in some areas. Finally, high water temperatures caused the deaths of around a billion different sea animals, including oysters, barnacles, and clams. Other affected animals included sockeye salmon, which died in droves from diseases that spread easily in overly-warm water. 

How to Prepare for Future Heatwaves

The June 2021 heatwave claimed lives, damaged infrastructure, destroyed crops, and impacted businesses. States in the northwest and northwest experienced sustained record-high temperatures. This experience taught states that they need to be prepared for future heatwaves. 

Hospitals learned that they need to better direct patients with heat stroke to less-crowded emergency rooms. They also learned that they need to stock up on ice and ventilators, as well as expand their air-conditioning capacity to help cool down patients. Hospitals in some states even purchased or rented expensive diesel-fueled portable chillers to pump in cool air. Meanwhile, local governments found out that they need to better warn their residents of the danger of heatwaves. This includes issuing warnings earlier and in multiple languages to try and reach the most people possible. During the June 2021 heatwave, residents in the Pacific Northwest rushed to purchase air conditioners. Only 53 percent of households in Washington state have air conditioning. Rising temperatures will likely see this number increase in future years. 

There are several tactics you can employ to stay cool in a heatwave. First of all, avoid going outdoors during the hottest parts of the day. Walk pets during the morning or at night, but otherwise, stay indoors if possible. Keep plenty of cool water and ice on hand, and stick to the shade if you must go outdoors. If you don’t have A/C, try running a fan. To make the fan cool, you can stick a bowl of ice in front of the fan, or dip a washcloth in cold water, wring it out, and drape the washcloth over the fan to increase its cooling effect. 

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