Reflecting on the March 2026 Heatwave in the Bay Area

Record high temperatures set during the past week in the Bay Area (Source: NWS Bay Area)

During the past week, many places in California (including the San Francisco Bay Area and Southern California) and the Southwest experienced unprecedented record-breaking high temperatures spanning across several days that would have been "virtually impossible" without the influence of climate change, according to a study. In the Bay Area, numerous records were set across various Bay Area communities, including Redwood City, San Rafael, San Francisco, and Oakland. Last Friday was the warmest day of the multi-day heat wave for the Bay Area, with the National Weather Service stations for San Rafael, Redwood City, San Francisco, Oakland Museum, Livermore, and SFO Airport setting new monthly record high temperatures for the month of March. Specifically, the record high temperatures for the National Weather Service (NWS) stations in San Rafael, Redwood City, San Francisco, Oakland Museum, Livermore, and SFO Airport on Friday were

• 92ºF in San Rafael (breaking the previous temperature record of 89ºF set just a day before)
• 94ºF in Redwood City (breaking the previous temperature record of 93ºF set just 3 days before)
• 90ºF in San Francisco (breaking the previous temperature record of 87ºF set on March 11, 2005)
• 91ºF in Oakland Museum (breaking the previous temperature record of 89ºF set just 3 days before)
• 91ºF in Livermore (breaking the previous temperature record of 90ºF set last year on March 25 and March 26)
• 89ºF in SFO Airport (breaking the previous temperature record of 85ºF set on March 25, 1953, a day before, and 3 days before)

All of the temperatures for these cities were warmer than the San Jose Airport's reported high temperature of 88ºF even though they are all located north of San Jose, and they (with the exception of Livermore) are generally less inland than San Jose. It was also surprising that Redwood City, which has the motto Climate Best By Government Test, could be warmer than not only San Jose but also Livermore, which has notably hot summers due to its inland location with a record high temperature of 116ºF set during September 2022 about 3.5 years ago. In fact, the NWS station for Redwood City had consistently higher temperatures during this heat wave than the one for San Jose (which is San Jose International Airport) as well as the highest monthly temperature record for March among at least the stations in the Bay Area that broke temperature records over the past week, tied with Salinas Airport (although Salinas is technically part of the Monterey Bay Area, just south of the San Francisco Bay Area). I do find it interesting though that the high temperatures on weather.com for San Jose were a few degrees warmer than the San Jose airport (including a 93ºF high last Friday in Downtown San Jose) during this heat wave and were comparable or slightly warmer than the weather.com temperatures for places like Redwood City, San Francisco, and Oakland. Meanwhile, Redwood City, Downtown San Francisco, and Oakland's high temperatures on weather.com last Friday were 92ºF (though I remember seeing Redwood City hitting 93ºF that day on weather.com), 81ºF (like Redwood City, I think I saw a high temperature warmer than the high temperature listed for San Francisco on weather.com that day), and 89ºF respectively. Despite these temperature differences between the reported high temperatures between NWS and weather.com for many places in the Bay Area, these temperatures are still well above average and are a stark contrast to typical March weather for the Bay Area. This heat wave marked not only the first time that I have witnessed 90ºF+ weather in March but also the first time seeing multiple days at 90ºF or above in the Bay Area during March. Sites such as weather.com and Accuweather showed my hometown of Palo Alto hitting 90ºF or above for 5 days straight last week.

Last Friday's high temperature for San Jose (93ºF - 5ºF warmer than San Jose airport's 88ºF)

Last Friday's high temperature for Redwood City

Last Friday's high temperature for San Francisco - notably cooler than the 90ºF high from the official NWS station but still well above average for this time of the year

Last Friday's high temperature for Oakland

High temperatures last week for Palo Alto via weather.com, Accuweather, and other weather sources.

Although not pictured, my Huawei Watch showed Palo Alto at 95ºF last Friday after connecting it to the Huawei Health App.

Given that many daily records and monthly records were set in this heat wave, with several of these cities setting a monthly record several degrees higher than their initial monthly record (prior to this heat wave, Redwood City's record high temperature for March was 89ºF set on March 31, 2011, while San Rafael's and Oakland's record high temperatures for March were both 88ºF - set on March 25, 1952 for San Rafael and March 11, 2005 for Oakland), I am concerned about these temperatures and am worried that they may become the "new normal" for Bay Area temperatures during this time of the year, especially if nothing is done to address climate change as a result of human activity. If nothing is done to curb fossil fuel consumption, greenhouse gas concentrations will continue to rise, which will lead to the average surface temperature on Earth to rise as well. Current estimates of how much average surface temperature could rise by the end of the 21st century range between 2ºC and 6ºC, with the predicted rate of warming for the next century being at least 20 times faster, according to NASA. NASA states that this rate of change is extremely unusual and that natural causes alone are not significant enough to explain the rapid warming seen in recent decades. While NASA states that greenhouse gases are long-lived and so the planet will continue to warm in the future (about 0.6ºC over the next century if greenhouse gases stabilized today), the amount of global warming that changes life on Earth depends on current human decisions. Personally, I believe that if more was done to address climate change years before, we probably would not have such an intense heat wave last week where coastal places like Redwood City, San Francisco, San Rafael, and Oakland were able to reach 90ºF or above. While there aren't any more 90ºF in the forecast for places like Palo Alto and Redwood City, forecast temperatures are still well above average for this time of the year (including forecast high temperatures for Palo Alto being 80ºF and 82ºF for today and tomorrow respectively according to weather.com). Additionally, the Bloomberg article "US Southwest Heat Wave Tumbles Records, Raises Fire Risks" by Brian K. Sullivan states that other areas in the US, including Las Vegas, Phoenix, and Downtown Los Angeles, may continue to break or tie records this week, and much of Texas, Oklahoma, and Kansas are under red-flag fire warnings. These record-breaking temperatures have their consequences, including California's snowpack experiencing its fastest late February-March melt on record, with the spring snowpack on track to being the second smallest (trailing behind 2015) since records began in 1950, according to Colin McCarthy's tweet on X. I personally saw many bugs around my house during this heat wave, with many these bugs still currently around even though my dad was able to kill quite a few of them (and I was able to kill one yesterday as well), and got a bite around the left side of my neck last Saturday when helping my dad with some outdoor house chores (I think that I may have gotten additional bug bites, though smaller than the one on my neck, yesterday as well). As someone who greatly dislikes bugs (including ones that fly around food and ones that bite people) and that there could be a major "bug boom" during spring and summer this year due to erratic winter weather patterns according to the Southern Living article "Experts Say That A Major 'Bug Boom' Could Be Heading Our Way - Here's What That Means" by Molly Burford, I believe that this is a wake-up call to realize that it is not normal to see many bugs during this time of the year. Given that bugs tend to thrive best in warm, dry weather (which accurately describes the weather during this past week's heat wave), it seems that the increase in bugs around my house is likely due to the 90ºF+ weather from the heat wave during this past week. I hope that the heat wave during the past week will allow others to realize that they should not only be aware that climate change is occurring but should also take actions to address climate change so that its consequences, including increased bugs, accelerating snowmelt (which can reduce water availability during summer), record-breaking temperatures (hundreds of thousands of people have died from heat-related causes each year), wildfires, droughts, and floods, can be avoided.

A weather.com forecast high temperatures for Palo Alto over the next 14 days - high temperatures may remain 70ºF or above until next Monday March 30

Fortunately, there are solutions that can prevent heat waves as severe as the March 2026 one from happening in the future as long as long-term climate change mitigation and localized heat resilience strategies are implemented. When it comes to long-term climate change mitigation, it is essential to reduce greenhouse gas emissions by burning less fossil fuels (coal, oil, and gas) and relying more on renewable energy (solar, wind, and other clean energy sources). A report from the Center for Global Sustainability at the University of Maryland School of Public Policy released September 2024 showed that "comprehensive, high-ambition climate action across all levels of government and all sectors of society and the economy can cut U.S. greenhouse gas emissions by 65% by 2035, compared to 2005 levels." However, to achieve this, the U.S. must set ambitious targets and engage in society-wide approaches to lowering greenhouse gas emissions in addition to transitioning to clean energy sources (including increasing solar and wind generation and expanding electric vehicle sales). The full report can be found at this link.

California is home to many refineries, including the Benicia Refinery in the Bay Area owned by Valero Energy. According to the CBS News's article "Valero will import fuel into the Bay Area after it idles Benicia refinery in April" by Jose Fabian and Amanda Hari, Valero will continue to provide the Bay Area with fuel even after idling its Benicia refinery in April. Personally, I think that it may be better for the Benicia refinery to convert itself into producing clean energy sources instead of importing gasoline to help make the environment more sustainable.

Additionally, the organization ClientEarth has been holding corporations accountable for "zombie wells" (these millions of abandoned polluting toxic wells on American properties in a widespread practice worsen climate change). They are also encouraging people to take action on urging Chevron to keep its promise and clean up its toxic mess by sending an email to the Chevron CEO.

The Draft of California's Extreme Action Plan (Protecting Californians Amidst Extreme Heat: A State Action Plan to Build Community Resilience) consists of 4 action tracks, with each action track having several goals to them. The action tracks and their goals are:

1. Build Public Awareness and Notification

- Goal 1: Build public awareness about extreme heat and its impacts through targeted communications campaigns

- Goal 2: Support actionable climate science and research to inform risk assessment and decision-making

- Goal 3: Improve accuracy and accessibility of heat modeling and data to inform decision-makers

2. Strengthen Community Services and Response

- Goal 1: Invest in social resilience

- Goal 2: Protect California's workers and economy from the impacts of extreme heat

- Goal 3: Support local planning and response measures to extreme heat events

3. Increase Resilience of our Built Environment

- Goal 1: Protect critical infrastructure

- Goal 2: Support heat resilient and cooler communities through regulations and codes

- Goal 3: Invest in cool buildings and surfaces

- Goal 4: Utilize science-based frameworks and tools

4. Utilize Nature-Based Solutions

- Goal 1: Promote nature-based solutions to reduce extreme heat risks

- Goal 2: Support nature's ability to withstand and adapt to increasing temperatures

- Goal 3: Reduce heat risk to water supply and systems

Urban heat islands are the fact the cities tend to be much warmer than their surrounding rural areas. To reduce urban heat island effect and energy demand, approaches such as expanding tree canopy, installing reflective rooftops, using permeable pavement, and opening cooling centers can be taken according to the APTIM article "Cooling Crisis: Why The 2025 Heat Emergency Requires Renewed Action" by Ella Dutton.

The Bay Area is home to several urban heat islands. For instance, Redwood City seems to be an heat island, which is a likely explanation of the much warmer temperatures recorded by the city's NWS station compared to the San Jose airport's NWS station during last week's heat wave. A CityTrees article from September 2023 mentioned that Redwood City had been struggling with its own urban heat island problem. Taking a look at Redwood City's tree equity score, there are many neighborhoods in Redwood City with a tree equity score in the 70s and 80s (a score of 100 means that the neighborhood has met tree planting goals). For instance, Redwood City's Census Block Group 060816102014 shows a tree equity score of 80 with a current canopy cover of 11% and a canopy cover goal of 30%. The score indicators consist of people of color (82%), children and seniors (35%), Linguistic isolation (11%), Health burden index (45), Heat disparity (+5.9ºF), People in poverty (31%), and Unemployment (0%).

Redwood City's Census Block Group 060816102014 tree equity score, current canopy cover, and score indicators

When looking at the insights to Redwood City's Tree Equity Score, the composite score is 84. The tree canopy cover is just 18% with 5 of 54 block groups having a tree equity score below 75. Additional insights include estimated total annual benefits, canopy trends, and tree equity score breakdown. For instance, in the tree equity score breakdown, neighborhoods scoring 80-84 are, on average, 2.0ºF hotter than the urban area average. Redwood City has 14 block groups with a score of 80-84.

Tree Equity Score Breakdown for Redwood City

Given that many neighborhoods in Redwood City can improve their tree equity scores, expanding tree canopy is one way for Redwood City to address its urban heat island problem. Redwood City is just one of the many examples of urban heat islands that can be addressed in the Bay Area. I would not be surprised if cities such as San Francisco, Oakland, and San Rafael also have urban heat islands that led them to record 90ºF+ temperatures during this past week's heat wave. The Axios article "Urban heat islands are worsening extreme temperatures in SF" by Shawna Chen, Rebecca Falconer, and Andrew Freedman mention urban heat islands in San Francisco (I will note though that to read the full article, one has to use their email to sign up for an Axios account).

map of San Francisco's urban heat island intensity

Overall, this past week's heat wave is statistically significant, including in the Bay Area. To prevent another heat wave as extreme as this one in the future, it is important to address climate change in several ways, including reducing greenhouse gas emissions and urban heat islands, transitioning to renewable energy, and expanding tree canopy.