Last summer was the hottest in two millennia. We won’t get any relief this year.
An overwhelming majority of Americans will experience above-average heat this summer, and temperatures in more than half of the contiguous United States are expected to top the historical average by at least 2 degrees Fahrenheit, according to AccuWeather. New York is expected to endure twice as many 90-plus-degree days as last year; Boston could experience up to four times as many.
Americans got a taste of what’s to come this week, with a blistering heat wave that began in the Southwest and has scorched the East Coast for the past three days. That heat may have come early based on the historical averages, but considering more recent trends, it’s right on track.
“The biggest changes that we have seen in recent decades is that the heat wave season has been expanding, starting earlier in the late spring and ending later into early fall, on average,” AccuWeather Senior Meteorologist Brett Anderson told Heatmap.
The northern Rockies, Great Lakes, and the Northeast are areas of particular concern, Paul Pastelok, AccuWeather’s Lead Long-Range Forecaster, told Heatmap. Those regions will likely experience less precipitation and more intense heat this summer compared to their historical average. “The Northern Plains and Upper Midwest are tricky,” Pastelok said. “Right now, this area is getting rain, but this could cut off by the very end of June into July, and turn around to dryness with the heat following.”
While temperatures will most likely peak in the interior Southwest — Nevada, Arizona, and New Mexico — by early July, the region can expect temperatures between 112 and 118 degrees until then. Monsoon season, which brings warm winds and rainfall inland, will likely arrive in late July instead of the usual late June, Pastelok said. Peak heat could come much later — anytime between July and September — for those in the Great Lakes, the Ohio Valley, and the Northeast.
The biggest “warm anomalies” are expected in the Southwest and central Rockies, the Great Lakes, the Ohio Valley and the Northeast, according Tom Kines, a senior meteorologist at AccuWeather. “We are looking at anomalies for the entire summer of +4 degrees (F) which is pretty significant over a 3 month period,” Kines wrote in an email to Heatmap.
Heat won’t be the only extreme weather this season. Drought could be severe, particularly in the Southwest — including parts of Texas, Oklahoma, and Kansas, where rainfall could come in below 50% of the historical average. That dry spell could intensify over the northern Plains, Great Lakes, and the Northeast later in the summer. The Gulf Coast, meanwhile, can anticipate a staggering 22 to 36 inches of rain this season — compared to its usual 15 to 24 inches — which will likely make flooding an issue.
After a wetter winter, meteorologists anticipated a slow start to the wildfire season in California and the Southwest. In fact, the number of wildfires this year is expected to come in below average: AccuWeather meteorologists predict 35,000 to 50,000 wildfires this year, compared to a historical average of about 69,000. Yet the fires in California also seem to have picked up speed a little earlier than normal. Last week saw more than two dozen fires in the state, perhaps heralding increased fire activity to come.
So how will we deal with all this? Northern cities, especially, tend to be less equipped to deal with extreme summer heat. In Boston, temperatures reached a record-breaking 98 degrees on Wednesday, a day after Mayor Michelle Wu declared a heat emergency. The city opened cooling centers this week in an attempt to minimize the number of heat-related medical emergencies.
Boston Green New Deal Director Oliver Sellers-Garcia told Heatmap that the city is bringing more government agencies into the heat management effort. The Fire and Parks departments plan to set up misting stations, and the city will continue to provide extra pop-up cooling centers in coordination with Boston’s Centers for Youth and Families. Those strategies, Sellers-Garcia said, “can have an instant benefit for someone, whether it’s just a super hot day and they have to get to work or it’s a declared heat wave.”
In Florida, people are used to chronic heat, Miami-Dade County’s Chief Heat Officer Jane Gilbert told Heatmap. Last year the county had 42 heat advisories (which happens when the thermometer reaches 105) and 70 warnings (110), Gilbert said, and this season is already proving more intense: May was the warmest ever on record in the state. To protect residents, the county has established a comprehensive public awareness campaign that targets those most affected by the heat, including outdoor workers, children, pregnant women, the elderly, and people with chronic illnesses. It also runs more than 30 cooling centers.
According to Gilbert, the goal is to educate people about the extent of heat impacts so they can make better choices — drink more water, find shade, limit physical activity — and protect their health. “We haven’t fully appreciated, historically as a community, how it impacts our lives,” she said.
Here’s what’s happened so far ...
Why cooling centers were closed last week
June 24: On Juneteenth, over 82 million Americans were under active National Weather Service extreme heat alerts — but, due to the national holiday, many publicly operated cooling centers were closed. While Boston had opened 14 new facilities in partnership with the Centers for Youth and Families, for instance, none of them stayed open Wednesday.
The same thing happened in New York, where more than 200 cooling centers were closed for the holiday, most of them libraries. While other heat preparedness measures were still in place — Gov. Kathy Hochul announced free admission for state parks — residents counting on a facility near home had to change plans last minute. On Sunday, New York turned 45 public schools into cooling centers, this time because the public libraries were closed due to budget cuts.
In Chicago, only one cooling center was open during the holiday. The lack of cooling spaces available sparked action from homelessness advocates, who are urging the city to offer more cooling centers that are open 24/7 and also to make those facilities available when the heat index is above 80 degrees Fahrenheit.
Because cooling centers are often multi-purpose spaces, data on their usage is limited. In Boston, 245 people visited cooling centers from June 18 to 20, the mayor’s office told me. New York City’s Department of Emergency Management could only say that six people visited four of the schools open Sunday.
The U.S. celebrated the official start of summer with a scorching heat dome
June 21: Communities from Kansas to Maine experienced record-breaking temperatures, with heat indices above 100 degrees Fahrenheit in some places. Cities including Philadelphia, Cleveland, and Burlington, Vermont opened cooling centers, and Boston and New York activated heat emergency plans. Schools in Buffalo, New York moved to half-day schedules for the week in response to temperature advisories.
The heat wave was expected to hold into the weekend, increasing the risk of emergencies. But ensuring that at-risk residents are aware of public services and heat mitigation strategies is often more difficult than simply providing amenities like cooling centers and air conditioners, Benjamin Zaitchik, a professor of climate dynamics at Johns Hopkins University, told Heatmap. “Preventing heat deaths — in principle, at least — is easy,” Zaitchik said. “It just requires good planning, good communication, good networks.”
The same heatwave afflicted much of the Southwestern United States the week before. Temperatures in Phoenix and Las Vegas exceeded 110 degrees, breaking records and prompting cities to issue heat advisories covering tens of millions of people. At a Trump rally in Las Vegas, 24 people received treatment for heat-related complications and six were hospitalized, The Guardianreported.
Hundreds died on the road to Mecca
June 14-19:More than 1,000 people died during the sacred Muslim pilgrimage known as the hajj as extreme heat gripped Saudi Arabia in mid-June. In Mecca, where temperatures exceed 120 degrees Fahrenheit, worshippers gripped umbrellas and water bottles to combat the heat. A study from 2019 predicted that hajj conditions would exceed an “extreme danger heat threshold” more frequently in the coming decades, especially when the pilgrimage — which is scheduled according to the lunar calendar — coincides with the warmer months of the year.
The death toll was about five times higher than last year, according to CNN.
Greece shut down
June 10: Passengers on a Qatar Airways flight passed out from heat as their plane sat on the tarmac at Athens International Airport. Flight 204, which was delayed for three hours with passengers stuck inside, experienced a malfunction in its air conditioning. Two days later, authorities shut down the Acropolis for five hours due to the 102 degree weather, which marked Greece’s earliest heat wave on record. Many schools were also closed for the day, and several air-conditioned spaces were opened to the public. Greece’s Health Ministry advised older people and those with chronic illnesses to stay indoors.
The intense weather continued throughout the weekend, and at least five tourists were reported to have died due to extreme heat.
Other parts of Southern Europe, such as Cyprus and Turk, have also suffered through heat waves this year. During the second week of June, temperatures in Cyprus exceeded 104 degrees every day and classes ended early. On June 14, some areas experienced their hottest June day ever, reaching 113 degrees. That same week, Turkey also battled record temperatures — they were 8 to 12 degrees higher than the average for the season.
Hundreds of millions voted in extreme heat
May and June: Both Mexico and India faced extreme temperatures during national elections.
Record-breaking heat waves have scorched Mexico since late March, causing blackouts, wildfires, heat strokes, and animal deaths. On May 25, Mexico City set a new heat record, with the temperature there surpassing 94.4 degrees, while other cities in the country registered even higher temperatures — well above 115 degrees. As of June 12, at least 125 deaths had been attributed to the heat, which has been made worse by an intense drought linked to El Niño. With reservoirs at less than 27% capacity, millions could run out of water by the end of this month.
World Weather Attribution, a research group that analyzes the degree to which climate change is causing extreme weather events, estimated that global warming has made extreme temperatures in the region 35 times more likely. “These trends will continue with future warming and events like the one observed in 2024 will be very common” in a world where average temperatures are 2 degrees Celsius higher than pre-industrial levels, the group stated in a release.
Despite sweltering conditions, about 100 million voters elected Claudia Sheinbaum, Mexico’s first female president, on June 2. In her victory speech, Sheinbaum, a climate scientist with a focus on energy engineering, said she will work to maintain the country’s energy sovereignty. While Sheinbaum has vouched to expand the country’s renewable energy, she has also been criticized for her support of Pemex, the state-owned oil company.
Two days later, on June 4, India re-elected Prime Minister Narendra Modi for a third term during the country’s longest-ever heatwave. By the time the weeks-long voting process wrapped, extreme heat had killed more than 100 people. In Uttar Pradesh, at least 33 poll workers died in a single day, CNN reported. In response, local governments have imposed measures to prevent water waste and protect construction workers. Yet, according to analysis by the Centre for Policy Research found in 2023, most of India’s heatwave policies are underfunded and fail to target the country’s most vulnerable groups.
More extreme weather hammered Mexico beginning June 20 as tropical storm Alberto brought torrential rain and flooding to the country’s east. AccuWeather meteorologists said the storm is just the start of a predicted intense hurricane season in the area. Most of India is still under heatwave alerts, but the weather is set to improve in the next few days as the monsoon finally advances after a week-long delay.
Drought is still threatening China’s wheat belt
May: Scarce rainfall and soaring heat have led to drought conditions that are threatening China’s food production and water supply. The provinces of Shandong and Henan — crucial to the country’s wheat production — are some of the most affected, and the State Flood Control and Drought Relief Headquarters has dispatched two disaster relief guidance teams. New technology, such as multi-functional seeders, and multiple reservoirs have been deployed to ameliorate conditions.
Also on Wednesday, the China Meteorological Administration reported that several regional weather stations recorded the highest temperatures ever in mid-June. Conditions are expected to worsen, as some Chinese provinces are expected to reach 111 degrees this week.
AccuWeather
Maxar Open Data Program via Gupta et al., CVPR Workshop Proceedings. Lütjens et al., IEEE TGRS
