Satellite view of smoke from wildfires in California and Oregon, 3 September 2017. Photo: Worldview / NASA

By Bob Henson 
3 September 2017
(Weather Underground) – The steamy, fiery summer of 2017 hit a new crescendo this weekend across the U.S. West, which is getting its hottest Labor Day weekend on record in many locations—and in some spots, the hottest weather ever observed. Overall, “this is the greatest statewide heat wave ever recorded in California,” proclaimed WU weather historian Christopher Burt on Saturday night. Burt based his conclusion not only on the heat’s intensity but on its widespread nature well beyond California’s usual scorching locations. Even an escape to the cool Pacific shore was pretty much futile, as easterly downslope winds funneled scorching air from the interior into coastal sections that are normally mild and sometimes chilly even in midsummer. Readings also soared above 110°F across California’s Central Valley, although such heat is not quite so unusual for late summer in that area.California’s Bay Area has been the focal point of the weekend’s most extraordinary heat. Temperatures soared to 106°F in downtown San Francisco on Friday and 102°F on Saturday. Friday’s reading was the hottest ever measured in downtown SF, where temperatures have been observed since 1874. Friday’s 106°F handily topped the previous record of 103°F from 14 June 2000, and Saturday was only the second high of 102°F in downtown history, matching 5 October 1987. “To put this in perspective, the average high temperature for the city these two days is just 71°F,” said Chris Burt, who lives in the East Bay region. “Friday night’s temperatures failed to fall below 85°F at several hill locations near me (I dropped to 81°).” He added: “It is so hot in our home I can hardly think. No air conditioning, of course.” Heat-related illnesses overwhelmed San Francisco hospitals on Friday, according to the Bay Area NWS office. It would not be shocking to see multiple Bay Area fatalities during this heat wave, given the multi-day intensity of the heat and the Bay Area’s lack of air conditioning.On the Marin County coast, the Point Reyes lighthouse station hit 91°F on Saturday, breaking its all-time record of 90°F from 3 October 1917, almost exactly a century ago. Remarkably, the temperature at Point Reyes at midnight Friday night was a sweltering-for-the-location 86°F—just 4°F below the previous all-time high.San Francisco International Airport hit 104°F on both Friday and Saturday. Although this has been reported as an all-time record for that measuring site, Burt says the airport actually reached 106°F on 14 June 1961, and 105°F on 14 June 2000. […]

The Air Quality Index (AQI) for the combined effects of ozone and PM2.5 pollution for 1 September 2017. Widespread areas of pollution in the red zone, “Unhealthy”, were recorded in California and Oregon, due to PM2.5 from wildfire smoke and the presence of high levels ozone from the extreme heat. Photo: EPA

Smoke from wildfires has been causing serious health problems in many western states over the past month. On Monday, Eugene, Oregon suffered its worst air pollution since the 1980s, when levels of fine particle matter (PM2.5) soared as high as 216 micro­grams per cubic meter. This corresponds to an Air Quality Index (AQI) in the purple range, “Very Unhealthy.” [more]

Heat, Smoke, and Fire Assault Western States: All-Time Record Heat in California