Unpacking the Latest Heat Wave in the West

When does summer end? It’s a tricky question, and while there is an astronomical answer (for the northern hemisphere, it’s the autumnal equinox on September 22), I’m not sure that most people think that way. Ten months ago, FiveThirtyEight published a fun, informal article about this very thing. We shouldn’t take this too seriously, but there was a roughly three-way-tie amongst respondents on what was the end of summer and the start of autumn. Of the responses, 26% stuck to the autumnal equinox. Another 25% pinned the end of summer on when the color of leaves start to change. Yet another 25% say that summer ends with Labor Day, which was September 5 this year. But I’m guessing that if you had asked Californians on Tuesday, September 6 if autumn had begun, you’d have been met with some combination of “no,” “heck no,” and death stares.

A Crisis Averted in California

Sacramento set a record high temperature of 116 degrees that day. Cities in the Bay Area also hit record highs, including San Jose at 109 degrees and Napa at 114 (I wonder what that will do to the wine crop this year?). Death Valley, California was only 125 degrees that day, which is nothing compared to the 127 degrees it was on September 2! That was the hottest September day ever recorded in Death Valley, FYI.

So yes, California hasn’t had the best weather recently. It’s more than just unpleasant, however. There were serious concerns about electricity providers needing to institute rolling blackouts across the state over concerns of grid stability. That’s what I want to unpack with this blog, but I’ll go ahead and tell you the end of the story - they averted catastrophe. As demand for electricity was threatening to exceed its supply on the afternoon of September 6, a FlexAlert text went out to the people of California, urging them to conserve electricity. It appears that enough people listened and most blackouts were avoided. If you want to really dig into the data of what happened that day, here’s the California ISO webpage with historic demand and supply. If you look at the “Demand Trend” graphic and set the day to September 6, you can see how electricity demand noticeably declined between 5:50 and 6:10pm local time. I guess demand response is an effective climate solution, huh?