How Extreme Heat Caught San Francisco by Surprise Over Labor Day Weekend

By Eric Simons, Bay Nature

They saw the heat coming for Northern California several weeks before it arrived. By mid-August forecasters and weather followers predicted that a hot blanket would smother the Western United States the first week in September. Every long and then medium-range forecast model painted the West Coast red. A week before Labor Day weekend, the National Weather Service (NWS) forecast office in Monterey — which rarely deploys adjectives — warned of “oppressive heat” over the upcoming weekend.

But the Weather Service, and everyone else, placed the epicenter of the heat inland. Forecasts focused on the potential for breaking all-time temperature records in the interior. There was talk of Livermore reaching 116 degrees, an all-time high only a degree short of the all-time record high in Las Vegas. There were also jokes on social media as people around the country saw the NWS-issued “excessive heat watch” for what weather app forecasts suggested would be temperatures in the high 70s in San Francisco. Even in the early morning on the Friday the heat wave began, the official NWS forecast discussion called for “upper 80s to mid 90s near the coast.”

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