Jackie Krentzman is a Bay Area-based writer and editor.   

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As the temperature soared to 100 degrees, residents in Riverside sought relief from the relentless sun by visiting air-conditioned malls and making their children play inside. Others held umbrellas over their heads as they went about their day.

A typical August day? Nope. It was March 19.

This March shattered heat records across California, forcing people to crank up their air conditioners and beeline toward cooling centers and shaded parks. It was just one more visceral reminder that as the climate warms, people suffer.

Over the past decade, cities across the state have accelerated initiatives to reduce the impact of extreme heat — defined by the U.S. Environmental Protection Agency as temperatures exceeding 95. In the city of Riverside, the number of 100-degree days nearly doubled from 2000 to 2024, according to the city’s Office of Sustainability. CalAdapt projects that by the year 2100, Riverside may experience 60-90 days above 102°F annually.

“Folks here are used to the heat — but not this much, this early and this often,” says Riverside Sustainability Manager Fortino Morales III.

Last fall, the city hosted an Extreme Heat Summit attended by representatives of local cities, hospitals, nonprofits, schools, and utilities. The city also conducted a tabletop exercise, simulating what happens to individuals, public health systems, and the built environment during an extreme heat event that lasts two weeks.

“We wanted to look at this nightmare scenario and see what can be done to prevent it and what to do when it happens,” says Morales, who calls extreme heat a silent killer, as symptoms may not be immediate. “It’s not like a tornado or a hurricane, where it’s obvious you should get inside,” he says.

The impact of extreme heat

Heat-related deaths and emergency room visits have risen in Riverside County over the last six years. A state analysis of a brutal September 2022 heat wave — one of the most dangerous waves in recent years — showed a 5% increase in overall deaths during that 10-day period, almost 400 more than expected.

According to Dr. Shunling Tsang, who serves as the Deputy Public Health Officer at Riverside University Health System – Public Health, many people in Southern California are used to days above 90 degrees and think they can handle the heat. But days and days of such temperatures will take their toll.

Tsang notes that the death rates from extreme heat are often undercounted. A death certificate may cite organ failure, but it could have been that extreme heat contributed to the death by overloading the organs. Furthermore, heat-related illnesses and deaths go well beyond those conditions we usually think about, such as dehydration, heat exhaustion, and heat stroke. The effect of heat on the body can be exacerbated by other conditions or medications.

“One of my patients is a 76-year-old gentleman with a history of hypertension and stroke,” Tsang says. “He is on medications, some of which are dehydrating, and in extreme heat situations, his body can’t react in the same way as somebody who is otherwise young and healthy. Different medications can alter your reaction to heat and can make you even more susceptible.”

Extreme heat does not impact everyone equally. Older homes and mobile homes may not have air conditioning units. Lower-income neighborhoods may not have the same tree canopies as more affluent ones. While most cities have cooling centers, people without cars can’t always reach them easily — or may need to walk a half mile in the hot sun to get there. Farm and construction workers don’t have the same heat relief options as those who work indoors.

V. Kelly Turner, a professor of geography and urban planning at UCLA and the associate director of the UCLA Luskin Center for Innovation, considers extreme heat a public health and environmental equity emergency.

“Heat is going to be the great un-equalizer in communities,” she says. “The quality of life in communities that have resources like shading, water features, and indoor cooling will be far greater than those that lack them. And some of the most pernicious impacts are cumulative and delayed, like the impact of heat on the neurological development of small children. … What might seem simple — going to work, getting your kids to and from school safely, for instance — might be really hard if you don’t have access to an air-conditioned car or indoor after-school care.”

Extreme heat not only stresses the human body. It also strains infrastructure: It puts a greater demand on the electrical grid, causing more frequent blackouts, buckles asphalt roads, and evaporates water supplies.

Heat buddies

The first step many cities have taken to address this crisis begins with messaging. People need to know what to do — and not do — to stay safe as temperatures surge. Cities have launched public health campaigns, reaching out directly to residents and teaming with community-based organizations that work with harder-to-reach populations.

Riverside is one of many cities that has emphasized a heat buddy system. It recommends that people — in particular the elderly, disabled, and other vulnerable groups — find a close friend, family member, or neighbor to check on each other during spells of sweltering weather. For those who work outdoors, such as farm workers and construction workers, that buddy could be a coworker.

“The idea is to look out for that person,” says Morales. “Sometimes we’re not our own best buddies. So, if you are doing outdoor activities, whether it’s for play or for work, ask each other regularly, ‘Did you drink enough water? Are you feeling okay?’”

Throwing shade and cooling pavements

One of the easiest immediate fixes is to plant more trees. The Kounkuey Design Initiative (KDI), a nonprofit founded by Harvard School of Design graduates in 2026, works with cities and other municipalities worldwide on improving public spaces. It is working in the Coachella Valley to plant more trees and add sun coverings at bus stops, schools, playgrounds, and shopping districts.

“Heat makes existing infrastructures unusable,” says KDI Community Principal Christian Rodriguez Ceja. “So, you end up with people avoiding public transit because there are no shelters at their stops or forcing their kids to play indoors instead of at a park.”

The design firm also teamed with the Coachella Valley Association of Governments (CVAG) and the Coachella Valley Housing Coalition to test different pavement technologies at affordable housing sites in Palm Springs, Desert Hot Springs, Coachella, and Indio.

“We know that material matters,” Ceja says. “For example, blacktop and asphalt absorb heat, which makes the surrounding area hotter, so we need to find alternatives.”

Riverside has also taken an aggressive approach. For decades, its public utility system has helped homeowners plant nearly 300,000 trees for free. In recent years, the city has opened more cooling centers, some of which are pet-friendly, and is exploring options to add solar and batteries to help reduce emissions and reduce energy consumption during high-heat days.

New and old ways to beat the heat

Some of the solutions for mitigating the urban heat island effect will take years to bear fruit. Palm Springs, one of the hottest cities in the U.S., is offering home energy assessments to help homeowners understand how they could make their homes more efficient and reduce emissions. It offers grants to low-income residents to replace their old air conditioning systems and add insulated, dual-pane windows that deflect heat more efficiently.

In 2024, the city received a Caltrans grant to fund a heat-and-shade study. The study will include a shade equity analysis, temperature assessments of urban heat hotspots, and an exploration of creative solutions like shade structures and nighttime safety improvements.

Palm Springs is amending its zoning code for the first time in 40 years, says Assistant City Manager Flinn Fagg, to help decrease the heat toll through changes to the built environment. This includes cool paving materials, adopting a tree ordinance to increase the drought-tolerant tree canopy, and finding out which roofing materials best deflect heat.  

Fagg says the city is leaving no stone unturned in its quest to reduce the impact of heat. “We are looking at everything, in great detail, asking things like, ‘How can we improve the experience of getting pedestrians from public sidewalks to the entrance of the buildings via shaded pathways?’”

Indio, deep in the Coachella Valley, has been proactively preparing for heat emergencies for years. Council Member Oscar Ortiz, who also chairs CVAG’s Energy and Sustainability Committee, says the city is implementing several strategies.

New public buildings, such as city hall, situate buildings to maximize shade throughout the day. Indio is also expanding and improving its urban greening to reduce heat and lower water use. For example, it pays people to remove turf gardens and replace them with native plants that produce shade.

Perhaps its most interesting initiative is bringing the past to the present. Indio recently launched a pilot program to return to older ways of sustainable construction, such as adobe or straw homes, that are more energy efficient (and fire resistant) than houses built with wood.

“We need to go back, and when appropriate, bring older strategies into the modern world,” Ortiz says. “How did people build shelters to reduce the heat effect? How did they use native plants over the centuries for cooling and water conservation? How did they grow food in extreme heat, with reduced access to water that we can adapt today?”

For cities, it’s a race against time to stay ahead of, or at least keep pace with, a warming planet. If nothing else, this past March’s heat spell should serve as a wake-up call. Ceja, who grew up in the Coachella Valley, remembers wearing a sweater in March as a kid and while trick-or-treating in in the early 2000s. He says cities can’t wait.

“This weird winter heat spell was a palpable reminder that we have gotten to the point where we can’t talk about the future of our cities without talking about how cities keep getting warmer,” he says.