The National Weather Service advised an estimated 450,000 residents in California to stay indoors on May 7 ahead of expected extreme heat, according to Newsweek. The warnings highlight rising concerns over health threats posed by extreme heat and climate change. California is experiencing a particularly hot year as temperatures rise worldwide, with the January 2026 to March 2026 baseline reaching 4.7 degrees above the 2025 average.
Since May 1, temperatures on the coast of San Diego County have maintained historic averages, while inland areas have surpassed records. Ramona reached a high of 100 degrees on May 10, exceeding the previous record of 91 degrees from 1981. Downtown San Diego documented its warmest February day in more than four years on Feb. 27 at 85 degrees. In March, residents saw a 16-day streak of daily temperature records, while Vista and Chula Vista experienced their highest temperatures to date.
According to researchers at the Scripps Institution of Oceanography, unusually warm sea surface temperatures may possibly increase humidity and heat conditions along the Southern California coast.
Alexander Gershunov, a researcher in meteorology at SIO, focuses on shifting weather patterns in a varying and changing climate.
“We had a super hot event at the end of February that wasn’t related to a Santa Ana wind event,” Gershunov said in an interview with The UCSD Guardian. “We do get dry heat at the coast in the wintertime that is associated with Santa Ana winds, but this one wasn’t and that was extremely unusual.”
Gershunov said changing ocean temperatures may be contributing to more humid coastal heat conditions across Southern California.
“Sea surface temperatures along the coast of California and particularly the Southern California bight are anomalously warm,” Gershunov said. “These warm sea surface temperatures would promote humid expressions of coastal heatwaves.”
According to Gershunov, humid heat is more difficult for the human body to tolerate because higher moisture levels reduce evaporative cooling and prevent temperatures from dropping significantly overnight. Atmospheric water vapor traps heat and limits nighttime cooling by absorbing and reemitting heat energy near the Earth’s surface.
Gershunov also highlighted that rising temperatures and longer-lasting heat waves are making extreme weather events more dangerous by increasing physical stress on the body and elevating the likelihood of heat-related emergencies.
Extreme heat is the most significant driver of reported deaths every year compared to any other weather hazard in the U.S., according to the California Office of Environmental Health Hazard Assessment. According to the Centers for Disease Control and Prevention, 2,000 people annually die from extreme heat in the U.S. In California alone, extreme heat was linked to 460 deaths between 2013 and 2022. Public health researchers found that extreme heat days were linked to a 66% increase in heat-related illness emergency room visits among both younger and older adults. San Diego County is seeing a steady 10-year upward trajectory in deaths from hyperthermia and heat-related illnesses, according to the California Health Alert Network San Diego.
Carlos Gould, assistant professor at UC San Diego’s Wertheim School of Public Health, said in an interview with The Guardian that rising temperatures are increasing health risks for vulnerable populations.
“We may be thinking, ‘I’m young and I’m healthy’ and so a hot day sounds like a nice day to go to the beach, but sometimes a hot day is a death sentence for vulnerable individuals,” Gould said. “One of the biggest challenges I can see moving forward are which interventions, which policy changes do work.”
Gould also explained that heat exposure is not evenly distributed across communities, with lower-income neighborhoods often experiencing higher temperatures due to reduced tree coverage and more heat-retaining infrastructure. Inadequate sleep and prolonged exposure to high indoor temperatures can create both short- and long-term health effects, Gould said.
“On average, neighborhoods that are poorer tend to be hotter,” Gould said.
He also noted that extreme heat does not need to break records to affect residents, particularly impacting vulnerable populations and people without reliable cooling access.
“Even when it doesn’t look like it’s a record-breaking day, even those 85-degree days, that pushes the body just a little bit,” he said.
San Diego’s recent heatwaves also amplify concerns over rising electricity costs. San Diego Gas & Electric’s rates increased earlier this year, up about 60% from 2020, continuing a broader upward trend that has raised residential energy bills across the county. SDG&E cites infrastructure costs and wildfire mitigation as contributing factors to the increase — expenses mostly required by state law and regulators.
SDG&E spokesperson Anthony Wagner said in an interview with The Guardian that a portion of customer bills go toward maintaining grid reliability. These infrastructure upgrades are designed to stabilize power during periods of extreme heat and high regional demand. Wagner said that the electrical grid experiences its highest stress during late afternoon and evening hours, when temperatures remain high and solar generation declines.
Wagner also noted that customers are using roughly 5% less electricity than five years ago as households adopt more energy-efficient appliances. However, he said grid maintenance costs remain fixed because SDG&E restructured residential bills in October 2025 to include a Base Services Charge regardless of how much electricity customers consume.
State climate forecasts project warmer-than-average conditions across much of California heading into the summer months.
