The California electrical grid survived — barely — a day of widespread, brutal heat on Tuesday. “This will be essentially the worst September heat wave on record, certainly in Northern California and arguably for the state overall,” UCLA climate scientists Daniel Swain said during a Twitter Spaces discussion Tuesday. “By some metrics, it might be one of the worst heat waves on record, period, in any month, given its duration and its extreme magnitude, especially in Northern California and especially in the Sacramento region.” As the mercury rose to 116°F in Sacramento, records fell across the state and electricity demand skyrocketed to a new all-time record of 52,061 megawatts, according to the state’s grid operator, known as CAISO.

Rolling blackouts were only avoided by California electricity customers — urged on by a well-timed text alert — voluntarily reducing their electricity demand during peak hours, along with rooftop solar panels and grid-scale batteries. Heat is the deadliest form of climate-related severe weather and compounds underlying societal inequities including racist housing policy; 42 million people were under excessive heat warnings Tuesday. The extreme heat, on top of the ongoing megadrout across the Western U.S. created extremely dangerous “red flag” fire conditions across parts of Idaho, Oregon, Washington, and the entire state of Montana. At least four people have been killed by fires across California this week.

(Heat & Grid: Washington Post $, AP, LA Times $, San Francisco Chronicle, San Francisco Chronicle, Reuters, Bloomberg $, E&E News, New York Times $, USA Today, Vox, New York Times $, Wall Street Journal $); Text message: Bloomberg $; Fires: The Guardian, New York Times $, Reuters; Heat records: KCRA Sacramento, Democracy Now, Fresno Bee; Climate Signals background: Extreme heat and heatwaves, Wildfires, Western megadrought)