Development to Meet San Joaquin Valley’s Population Growth, Extreme Temperature Must be Climate-Smart

November 6, 2019 | 5:42 pm
Jamesine Rogers Gibson
Former Contributor

The San Joaquin Valley – breadbasket of the nation – is among the fastest growing, yet poorest regions in California. It will need to undergo significant development to accommodate another projected 1.7 million people over the next three decades (for a total of 6.1 million). But population numbers are not all that will rise. Temperature and precipitation extremes will increase in frequency and severity as a result of unabated climate change.

Any economic, housing, and infrastructure-related development efforts in the region, like Governor Newsom’s Regions Rise Together, should plan for these changes, since they will affect the economy and the health, safety, and quality of life for workers and families over the coming decades. Efforts also should address underlying inequities that render many of the region’s residents among the most vulnerable populations to the impacts of climate change.

Hotter Days and Nights

Living in the San Joaquin Valley means living with heat, where historically July temperatures can regularly be 95-100°F. Over the next 30-70 years, it will get even hotter due to heat-trapping carbon emissions, primarily from the burning of fossil fuels. These higher temperatures will place additional pressure on the region’s critical infrastructure and vulnerable populations, like children, the elderly, and outdoor workers. Prolonged exposure to extreme heat can be dangerous, resulting in heat-related illness and aggravated chronic disease. Hotter days and nights can also stress the infrastructure that people rely on to keep cool when it is dangerously hot outside, like the electricity grid and buildings.

To better understand future conditions in the Valley and their potential impacts on people and infrastructure, the Union of Concerned Scientists (UCS) analyzed high-resolution climate model data for three future scenarios. We also used GIS data from the California Energy Commission for the electricity grid to determine the locations of critical electricity grid infrastructure.


The growth or reduction of global heat-trapping emissions in the coming decades will determine how much more frequent extreme heat events will become in the United States. This analysis examined three scenarios: “no action,” “slow action,” and “rapid action” to reduce global emissions. Rapid action is consistent with the goal of the 2015 Paris Agreement. Source: UCS


We found that:

  • With the no global action to reduce emissions, maximum daily temperatures (median) would increase across the San Joaquin Valley by 5-7°F by mid century and by 8-11°F by late century compared to historical levels. (The historical baseline for comparison is the median from eight climate models of the maximum daily temperature over 1975-2005.)


  • Nighttime low temperatures, which have already risen up to four times faster than daily maximum temperatures, will continue climbing in a warming climate, as shown below. The implications could be serious for people and infrastructure depending on low overnight temperatures to cool off. For instance, the high illness and mortality rates during the July, 2006 heatwave stemmed largely from warm nighttime temperatures. Transformers also heated up from heavy electricity use, and then failed to cool down due to “warmer than usual” air, causing circuit breakers to trip and cut off power.


  • Hotter days and nights could result in the electrical grid in the San Joaquin Valley – which is critical to residents’ health, safety and quality of life and a functioning economy – operating closer to its limits, with less cushion to absorb disruptions and prevent service outages.
Bar graph of Rising nighttime temperatures in the SJV

Nighttime low temperatures will rise significantly if no action is taken to limit climate change. Maximum temperature values represent median values across the entire year. Data source: Pierce et al., 2018.

But it’s not just the heat that matters. As humidity rises, the body cannot cool itself as easily and, if someone remains overheated, the risks of heat-related illnesses (heat cramps, heat exhaustion, and heat stroke) and death grow. While the warm season has typically been arid, nighttime heat waves in California have become more humid.

A recent UCS analysis – the Killer Heat report – projected the average number of days above select heat index values (or “feels like” temperatures combining heat and humidity) between now and the end of the century. At a heat index of 105°F, healthy adults are at heightened risk of heat-related illness, not to mention more vulnerable populations like children, elderly adults, pregnant women, and people with underlying conditions. The number of 105°F days would increase significantly across the San Joaquin Valley, especially compared to most other parts of California, as shown below. For example, Fresno historically experienced an average of 3 days per year above a heat index of 105°F. Residents would be exposed to nearly 1 month per year by midcentury and an average of almost 2 months per year with such heat by late century if global heat-trapping emissions continue on their current trajectory.


The number of days exceeding a heat index of 105° F would drastically increase in the San Joaquin Valley by mid-century if no global action is taken to reduce heat-trapping emissions. Reliable infrastructure for cooling, like cooled buildings, the electricity grid, and ‘cooler’ landscapes, will be critical to the health and safety of San Joaquin Valley residents.


In a new UCS analysis which will be released this week, we also found that rising temperatures would reduce the window of time that it is safe for children to be active outdoors, potentially disrupting health-promoting activities like exercise, further interrupting everyday life, and reinforcing the importance of reliable cooling and climate-safe infrastructure and school facilities.

Water Scarcity and Precipitation Whiplash

Years of drought and water contamination have left many rural families in the San Joaquin Valley with limited or no access to clean water. Reliable, potable water supplies could become even scarcer as the mercury rises. By 2050, hotter temperatures could reduce the average amount of water supplied by the Sierra Nevada snowpack – the state’s largest natural reservoir – to two-thirds of its historical levels, and less than one-third by 2100, if emissions continue rising throughout the century. The region relies heavily on this snow-based reservoir for its water supplies. “Precipitation whiplash” would also increase, with more exceptionally dry years followed by extraordinarily wet years, and shorter wet seasons. Dry conditions will also place increasing pressure on another major source of California’s water, its groundwater. If not managed well, it could result in overpumping groundwater and increased water contamination.


 Lake Oroville reservoir during drought.

Much of California’s Central Valley already experiences extremely high levels of water stress. Precipitation whiplash will increase over the century due to climate change, with droughts becoming more frequent and intense.

Worsened Air Quality

Ozone and particle pollution levels in the region, which are currently among the nation’s highest, could worsen over the coming decades due to global warming. Warmer days are more conducive to ground-level ozone formation. Hotter, drier conditions could also increase the risk of wildfires and their toxic smoke. One study estimated a 77 percent increase in average acres burned statewide by 2100, including the Sierra Nevada mountain range and the coastal ranges that border the San Joaquin Valley. In addition, these fires could degrade water quality and damage several high voltage lines that run through the California Public Utilities Commission’s elevated and extreme fire-threat areas in the Valley.

Farmworkers pick tomatoes at Taylor & Fulton Tomatoes in Immokalee, Fla

Outdoor workers in the San Joaquin Valley are exposed to unhealthy levels of air pollution. For example, many farm workers continue working in the fields when skies fill with smoke.

Hotter, drier conditions from more prolonged or severe droughts could contribute to enhanced conditions for spreading the soil-borne fungus that causes Valley fever. Once inhaled, it infects the lungs and is potentially deadly. The fungus is endemic to the San Joaquin Valley and disease rates are increasing here and other parts of California.

San Joaquin Valley Residents Are Already Vulnerable 

The extent to which these impacts will harm the region’s residents and economy relies in part on their vulnerability. For example, people experiencing poverty are particularly susceptible to heat-related illness. They typically live in the hottest parts of cities and in older buildings, which tend to heat up more quickly than newer buildings. Social and financial inequalities could prevent their access to cooling centers, healthcare, and air conditioning.

Despite boasting seven of the ten highest agricultural producing counties and the top oil producing county in the state, the region is characterized by extreme poverty. The unemployment rate is 6-10 percent depending on the county, compared to 4 percent statewide. More than 1-in-3 to 1-in-4 children live in households below the federal poverty lines (compared to a statewide average of 1-in-5). Most of its census tracts rank in the upper quartile of California’s disadvantaged communities.

Over one-third of the region’s 4.4 million residents live in major cities, like Fresno, Bakersfield, and Stockton, which tend to be hotter than more rural areas because of the urban heat island effect. Another 300,000 people reside in rural unincorporated areas with limited services and often dilapidated infrastructure. Decades of underinvestment and disinvestment has contributed to the inadequate and deteriorating state of infrastructure in many other low-income communities, communities of color, and tribal communities. More than half of the Valley’s residents are Hispanic or Latino (53 percent compared to roughly 40 percent statewide), while African-Americans and Asian Americans constitute 4 percent and 8 percent of the population, respectively.

Outdoor workers, children, and people with underlying health conditions are more vulnerable to heat-related illness as well. There are more than 200,000 farmworkers, and at least 55,000 construction and extraction workers in the Valley. Most of the region has higher childhood asthma and obesity rates than the statewide average.

Successful Economic and Infrastructure Development Efforts Must Be Climate-Smart

Sweltering temperatures, water shortages, and smoky skies will directly affect the economy, whether through workers’ health and productivity, availability of vital resources like clean water and air, or the ability to attract new businesses and families to the region. The SJV should seize the opportunity provided by its projected growth and current economic development efforts to prepare for a warmer future and a cleaner economy.

Community-based organizations and other non-profit organizations have been working for decades to improve life in the Valley on issues like improved housing, clean energy and water access, and better air quality, among others. UCS is grateful for their work and dedication to the people of the SJV. Some local governments are also making strides, and there’s so much more to do.

It is not possible or practical to avoid every negative effect of climate change on people, infrastructure, and resources. Risks can however be minimized – and taxpayer, ratepayer, and corporate dollars spent more wisely – by ensuring the Valley’s growth is climate-smart, that is resilient, low-carbon and equitable. The result would be transformational. Only if investments in communities and infrastructure prioritize and operationalize equity and climate resilience, alongside carbon reductions, will the regions of California, including the San Joaquin Valley, truly be able to rise together.

UCS will release two more blogs focused on schools and the electricity grid in the San Joaquin Valley over the next couple days.