Since the 1950s, Phoenix has seen a change in population that skyrocketed from 100,000 residents to now 1.62 million, said Erinanne Saffell, Arizona state climatologist. Along with the trend of increasing residents, the temperature has increased by 4.5 degrees on average over the past 70 or so years.

Not only are the maximum temperatures increasing but so are the minimum temperatures, said Rosanne Albright, environmental programs coordinator for Phoenix. The average nighttime temperature has increased by seven degrees since the 1950s, moving from 57 to 64 degrees.

The buildup of heat is because Phoenix has buildings and groundcover that hold onto that heat and release it slowly at night, making nighttime temperatures higher than normal, which leaves community members vulnerable, Saffell said.

“We have seen hundreds of cases of heat-related deaths in the past two decades with those numbers increasing as a consequence of the record heat,” Albright said.

According to the Arizona Department of Health Services, there were 2,414 heat-related emergency department visits in 2020. The number of heat-related deaths has increased since 2019, going from 283 to 522 in 2020.

Record-breaking temperatures were seen on June 15, 2021, as the high reached 118 degrees, Saffell said. That week the community experienced a heat wave that exposed people to extreme temperatures for several days in a row, posing health and safety concerns.

Not only can the heat send people to emergency rooms, but it also has direct effects including not sleeping well, not learning well and difficulty engaging in physical activities, Albright said.

“It is important from a public health perspective to do as much as we can to keep our neighborhoods cool and comfortable,” she said.

Phoenix this year has implemented its second climate action plan since 2009, Albright said. The 2021 plan is focused on government operation as well as the greater community within the boundaries of Phoenix.

“The time between 2009 and 2021 has given us good data and now it is good timing for a community wide action plan,” she said.

“When we put our climate action plan together, we made a conscious effort to think about ‘what do we face here in Phoenix,’” Albright said. “Air quality, food, heat and water are really tailored specifically to the residents’ concerns.”

Saffell relates the rise in temperatures to anthropogenic climate change meaning the way energy is used in urban environments has changed.

“When we look at the urban heat island it has absolutely changed our climate system,” Saffell said.

According to the U.S. Environmental Protection Agency, heat islands are urbanized areas that experience higher temperatures than outlying areas. The buildings that encompass Phoenix hold onto the heat making it a warmer region than nearby communities, Dr. Saffell said.

Phoenix residents should consider public transportation, carpooling, rideshare and improving personal water conservation to help combat the continuous rise in temperatures, Albright said.

“It is important not to sell it short and respect heat in Arizona because it can kill,” Saffell said.

Peyton Tovey is a student at the Walter Cronkite School of Journalism and Mass Communication at Arizona State University.