SANTA ROSA -- Forecasters predicted historic winds.

And they didn't exaggerate.

Northern California was being battered Sunday morning with extreme Diablo winds. The National Weather Service clocked a gust of 93 mph near Healdsburg, which is now threatened by the Kincade fire. The winds caused the fire in Sonoma County to explode overnight, prompting evacuations in Santa Rosa and south to Bodega Bay.

The Diablo winds came to Santa Rosa early Sunday. The whistles and flutters that announced their coming just past midnight quickly turned into long, angry howls and gusts that rattled buildings.

By 4 a.m., new evacuation orders and warnings came out for more of Santa Rosa, leaving large swaths of the city under threat. The area west of Charles M Schulz Sonoma County Airport was put under mandatory evacuation. Sutter Hospital nearby evacuated the night before. Now it was Kaiser's turn and ambulances snaked the lot loading patients.

The duration of the extreme wind event, known in the Bay Area as Diablo winds, was forecast to be roughly 36 hours, from Saturday evening around 8 p.m. into Monday morning, with isolated gusts of 65 mph to 80 mph in the highest peaks in the North Bay.

Not only will winds be bad, but the air will be quite dry -- relative humidity levels are forecast to fall between 15% and 30%; anything in the teens and 20s is really dry.

Temperatures are forecast to drop from midweek levels, which reached the 90s as the Kincade fire burned out of control on the northern edge of Sonoma County, destroying dozens of structures; in the North Bay, highs were forecast to fall into the 80s on Saturday and the 70s on Sunday, said weather service meteorologist Anna Schneider. But the falling temperatures won't make much difference; the hot weather this week just dried out vegetation even more.

The Diablo winds coming to Northern California this weekend are meteorologically identical to the Santa Ana winds of Southern California. Both come from the northeast and are fueled by high-pressure air over Nevada and Utah seeking a path through the Sierra Nevada and Coast Ranges or Transverse Ranges to fill lower-pressure voids on the coast.

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