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‘Extreme Heat’ forecast provides California temperature projections for mid- and late-century

A new online tool introduced earlier this month allows users to see what climate models say about their own community, down to their street address.|

We think we know hot.

But imagine temperatures surpassing 100 degrees 30, 40, even 50 days a year, or adapting to a climate where one day out of every three is above 90.

Wine Country will fare far better than Central and Southern California, but the face of the not-too-distant future has a sunburn and a sweaty brow, according to a recent forecast of community conditions around California.

A new online tool introduced earlier this month allows users to see what climate models say about their own county, community, ZIP code, census tract, even their neighborhood — down to their street address.

Sonoma tops the list of Sonoma County’s hottest cities, with the potential for 39 days a year at 100 degrees by late century, defined as the year 2070-2099 by the California Healthy Places Index: Extreme Heat Edition.

But by midcentury — 2035 to ‘64 — residents there will be looking at 23 days a year above 100 degrees and 90 days above 90 degrees.

Cities in neighboring counties — Ukiah, Calistoga, Lakeport and Clearlake — are projected to have even more extreme heat, raising greater concerns not just about sheer discomfort but about public health and safety.

“I don’t think people realize that extreme heat is actually the number one killer of any extreme weather” — more than hurricanes, more than flooding, more than wildfires, said John “Jake” Dialesandro, a postdoctoral research fellow at the UCLA Luskin Center for Innovation who focuses on climate science. “People don’t really think about the consequences of heat.”

No recovery time

Circumstances around the globe are increasingly forcing us to do just that, however, with staggeringly high, deadly temperatures in India and Pakistan this year, record highs in China, blazing conditions across Europe (which melted and buckled asphalt roads and runways in Britain), and oppressive heat affecting tens of millions of Americans across much of the country this past week.

“What we’re seeing is not just hotter days,” said Sonoma County Director of Emergency Management Chris Godley. “The real concern is that the heat’s not going to go away at night. The temperatures don’t dip, which is what is called the recovery phase.”

Scientists also are exploring changes in sea breezes and the degree to which ocean fog is less likely to extend over the land, providing less of what Godley described as that “Bodega Bay air conditioning” that tends to cool inland Sonoma County down at night.

The combination would mean people exposed to extreme heat over multiple days would more likely suffer health problems such as heat exhaustion or heat stroke without focused adaptation and precautions.

There are also complicating factors that make extreme heat dangerous, particularly for the young and the old, those already suffering from preexisting illness, outdoor workers, pregnant people, the homeless and those in confined, non-air conditioned settings.

Heat can compound existing health conditions in some people or exacerbate adverse atmospheric or environmental conditions, such as low-level particulate matter, Godley said.

Vectors, like insects and other animals, also may alter their range as traditional habitats become unsuitable, bringing disease-causing organisms to new areas.

“The way I think about heat is through the lens of hazard assessment,” Godley said.

And though concerted efforts are under way around much of the globe to substantially draw down carbon emissions, the human race already has ensured temperatures will rise for several decades through emissions already accumulated.

“The book’s already closed on that,” Dialesandro said, “so mitigation is our number one priority right now.”

Projecting the upper limits

The California Healthy Places Index: Extreme Heat Edition is the latest effort to project the upper limits in California — and prod users to prepare for it. It is the product of a partnership between the UCLA Luskin Center and the Public Health Alliance of Southern California, a coalition of 10 local health departments in Southern California representing more than 60% of the state population.

The first version of the Healthy Places Index, launched in 2018, offered a public platform overlaying demographic, economic, environmental, health and other data to inform policymakers and advance health equity in California.

The Extreme Heat Edition, introduced in July, adds in projected heat exposure as well as place-based information on factors like tree canopy coverage, resilient housing, heat-island impacts and access to parks. Additional information includes data on the degree to which the population is vulnerable due to age, medical condition, economics or other reasons.

The platform also offers links to a variety of grant programs and other resources for building weatherization, solar power installation, neighborhood greening, energy-efficient air conditioning, low-carbon transportation alternatives, planning assistance and other help for schools, local governments and low-income or disadvantaged homeowners.

The idea is to empower public agencies and community groups to target mitigation efforts where they are most needed in pursuit of climate justice, Dialesandro said.

“Heat is kind of invisible,” he said. “They wanted to make a visualization of how these scenarios are going to play out in the future and where we are now.”

The Healthy Place Index is not the only resource for this kind of information. Climate resiliency planning has focused on future forecast conditions, potential mitigation measures and climate justice issues for some time.

Cal-adapt.org provides access to localized climate projections, for instance, while the California Heat Assessment Tool, funded by the California Natural Resources Department, overlays projected health-impacting heat events with data on social vulnerability, health and environment information.

There’s also the new federal web site, heat.gov, which provides abundant information on weather conditions and health, focusing new attention on the risks of extreme weather like wildfires, droughts, disease, and high heat.

The HPI heat edition’s capacity for plugging in an address and creating a detailed data profile sets it apart, painting “a more visible picture of the likely scenario we’re heading toward,” Dialesandro said.

A still-evolving tool

Barbara Lee, director of climate action and resiliency for Sonoma County, said the Extreme Heat Index is a useful tool for the kinds of planning the county has under way to help residents confront the future.

Though much of it is still evolving, the county is deeply involved in developing emergency planning, resilient land strategies and programs for aiding residents in doing the kind of individual work that will help them prepare their homes to handle temperature extremes.

Part of the focus is preparing for extreme heat events, which, as Lee noted, often go hand-in-hand with high-fire danger and intentional power shutdowns just when buildings most need cooling.

That means increasing outreach and education about the risks of extreme heat exposure, the signs of trouble and simple but necessary steps like consuming enough water to replace what’s lost because of heat and/or activity, Lee said.

It also means ensuring people have somewhere to go to find relief — whether it’s a well-insulated or air-conditioned building, a shady spot, a leafy tree or some other greenery.

One project involves preparing the Santa Rosa Veterans Memorial Building, which currently has no air conditioning, to serve as a high-efficiency, solar-powered cooling center or shelter, if needed, equipped with storage batteries and backup generators, said Jane Elias, the county’s energy and sustainability program manager. The county also is working to acquire portable systems that could be deployed strategically around the county in the event of emergency, including to help power cooling units, she said.

The Energy and Sustainability Division offers homeowner workshops on a host of climate resilience topics, from solar and battery storage basics to funding improvements. The county offers financing for more than 100 kinds of improvements, including things like air sealing, insulation, cool roofing and upgraded windows. It can help with grant programs tailored to single-family, multifamily and commercial entities, Elias said.

In the natural environment, the county recently circulated a draft of its Sonoma County Climate Resilient Lands Strategy, with a goal, among many, of bringing climate resilience to those most at risk, in part through natural buffer zones, urban stream restoration and support for regenerative agriculture.

The county already is pursuing funding to help plan a series of connected green corridors that would be run through the built urban environment where there is intrinsically less access to open space, Lee said.

“It doesn’t need to be a single long park,” she said, but more “like pearls on a string,” with a park next to a community garden next to a bike trail or farm.

Conceptually, they would run east-to-west through the Larkfield/Wikiup and Cotati/Rohnert Park areas, as well as from northeast Santa Rosa toward the Springs area west of Sonoma. Another corridor is envisioned from northwest Santa Rosa south to Rohnert Park.

Lee said the county would like to pull residents from affected areas to work on the plans with help from community groups and nonprofits so there’s true public engagement.

“We know that we are going to experience those levels of extreme heat,” Lee said. “We will experience them here locally, in the future, and what we’re doing now is figuring out all the places we need to think about and continue to deliver the services we need to deliver.”

You can reach Staff Writer Mary Callahan at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.

City/Community Days/year above 100, 2035-2064 Days/year above 100, 2070-2099 Days/year above 90, 2035-2064 Days/year above 90, 2070-2099
Bloomfield 12 22 60 85 1/2
Bodega Bay 10 18 1/2 53 1/2 77 1/2
Boyes Hot Sprgs 23 1/2 39 90 117
Calistoga 26 45 1/2 96 122
Clearlake 31 54 1/2 101 122
Cloverdale 21 35 85 1/2 109
Cotati 10 1/2 19 55 80 1/2
Dillon Beach 12 21 1/2 61 89
Geyserville 30 48 1/2 107 134
Guerneville 7 14 49 71
Healdsburg 20 1/2 32 87 112
Lakeport 38 61 1/2 106 125
Napa 14 23 1/2 67 96
Novato 6 12 1/2 41 65 1/2
Penngrove 11 19 1/2 56 1/2 83
Petaluma 8 1/2 16 48 73
Occidental 10 18 1/2 53 77
Rohnert Park 10 1/2 19 54 1/2 79
Santa Rosa 12 1/2 21 1/2 60 84
Sebastopol 11 1/2 21 57 1/2 82 1/2
Sonoma 23 1/2 39 90 117
Windsor 17 28 79 104
Ukiah 29 1/2 51 97 118
Forecast high temperature days per year for select cities and communities

Mary Callahan

Environment and Climate Change, The Press Democrat

I am in awe of the breathtaking nature here in Sonoma County and am so grateful to live in this spectacular region we call home. I am amazed, too, by the expertise in our community and by the commitment to protecting the land, its waterways, its wildlife and its residents. My goal is to improve understanding of the issues, to find hope and to help all of us navigate the future of our environment. 

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