Aug 18, 2022 - News

"Hot days" forecast to rise in San Francisco

Note: Shaded counties are those that will, on average, have 0.5 days or more at or above a 125F° heat index in 2053; Data: First Street Foundation; Map: Axios Visuals

An "extreme heat belt," where temperatures feel like 125°F for at least one day per year, could emerge from Texas to Illinois over the next 30 years, according to a report published this week by the nonprofit First Street Foundation.

Zoom in: Four counties in California's southeast region — Imperial, Riverside, San Bernardino and Inyo — are also expected to reach extreme heat levels at least one day every year by 2053.

Threat Level, via Axios Generate's Andrew Freedman: The report, based on First Street's peer reviewed heat model, shows that the number of Americans currently exposed to "extreme heat" — defined as having a maximum heat index of greater than 125°F — is 8 million.

  • However, due to the anticipated warming during the next three decades, that number is expected to balloon to 107 million people.

In San Francisco, extreme heat isn't necessarily a problem.

  • The report estimates that by 2053, the city will have zero days with a heat index over 100°F.
  • There isn't even supposed to be a day when it's over 90°F.

Yes, but: The report considers a "hot day" in San Francisco any day that reaches a "feels like" temperature of over 77°F.

  • The number of hot days in the city is expected to increase from seven this year to 16 by 2053.

Hot days in nearby Sacramento — which hit a "feels like" temperature of over 102°F — are expected to more than double over the next 30 years.

  • Similarly, in Fresno, days with a heat index over 105°F will likely jump from seven in 2023 to 17 by 2053.
  • With heat levels rising across the state, the report estimates that California will spend $574 million more on electricity used for air conditioning by 2053 — the biggest increase over the next 30 years for any state in the country.

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