Bay Area heat to return briefly, but dry lightning looms as threat

"Then just when those temperatures come back down, another ominous development is in the making. "We could have dry lightning," National Weather Service meteorologist Roger Gass said. Indeed, the chances for one of the more extreme weather weeks the region has experienced this summer will get rolling with temperatures that will be hotter than normal early in the week but not as blazing as they were in early September a year ago."

""It's gonna warm up but it's not going to be too incredibly hot," Gass said. "It's gonna be anywhere from 5 to 15 degrees above average, and probably 5 to 20 above normal for the overnight lows." Temperatures are expected to peak Tuesday with Concord and Livermore expected to hit 97 degrees, San Jose 92, Oakland 85, Santa Cruz 83 and downtown San Francisco 75."

"On Wednesday, high temperatures are expected to be about 2-3 degrees cooler, before falling sharply in the evening, as moisture from Tropical Storm Mario off Mexico's Pacific Coast brings upper-level moisture, Gass said. That moisture in the upper levels of the atmosphere then will mix with the lower drier air that is creating the high temperatures. That combination is a bad mix, because it creates instability and electrical volatility in the atmospher"

Bay Area temperatures will rise briefly this week, with inland locations potentially approaching triple digits and overnight lows 5 to 20 degrees above normal. Concord and Livermore could reach around 96–97°F, San Jose about 90–92°F, Oakland mid‑80s, Santa Cruz low‑80s and downtown San Francisco mid‑70s. Moderate heat risk is expected across much of the region, and people are urged to stay hydrated and not leave children or pets unattended in vehicles. By Wednesday, upper‑level moisture from Tropical Storm Mario will mix with hot, dry low‑level air, creating atmospheric instability and raising the risk of dry lightning.

Read at The Mercury News