The most powerful winds to tear across California in nearly 15 years kept 9-year-old Dalen Guyton up late into the night. Then, around midnight, came the boom.

The great yawning tree that stood next to his grandmother’s house, the one with the rope swing he and his sisters played on, had toppled, coming within inches of their one-story home.

On Thursday, the siblings stood out front surveying the damage, like thousands across the West where high winds toppled countless trees, knocked out power to hundreds of thousands and brought gusts of 123 mph.

“If she pays someone to clean it up, it’s not going to be a good Christmas,” said the boy, who was wearing a Santa hat. “She’s not going to be able to get any presents.”

The National Weather Service called Southern California’s winds Wednesday night a once-in-a-decade event, and it’s not over. Winds were expected to pick up again Thursday night though they won’t be as fierce.

In the mountains, winds were expected to gust up to 65 mph into Friday morning and 50 mph in the valleys.

High wind warnings and advisories were also issued for Utah, Nevada, Wyoming, Arizona and New Mexico. The blustery weather is expected to eventually hit Oklahoma, Missouri and Indiana.

The storms were the result of a dramatic difference in pressure between a strong, high-pressure system and a cold, low-pressure system, meteorologists said. This funnels strong winds down mountain canyons and slopes.

The winds reached 123 mph at a ski resort northwest of Denver and topped 102 mph in Utah.

California, however, was the hardest hit, with more than 200,000 utility customers without power. The gusts were blamed for toppling semitrailers and causing trees to fall on homes, apartment complexes and cars.

In some neighborhoods, concrete light poles cracked in half. Darkened traffic signals and fallen palm tree fronds and branches snarled traffic. At a Shell station, the roof collapsed into a heap of twisted metal.

“It was a terrifying ride for me, coming here in pitch dark … and watching motorists take no notice of lights being out,” said Bob Spencer, a spokesman for the Los Angeles County Department of Public Works.

Bill Patzert of NASA’s Jet Propulsion Laboratory, lives in Sierra Madre and like hundreds of thousands of people across the region, lost power at his home. A heavy tree limb blocked his driveway.

He estimated winds peaked between 80 to 90 mph in his neighborhood overnight.

“It was like being in a hurricane. I thought I was going to blow away,” he said. In heavily damaged Pasadena, schools and libraries closed and a local emergency, the first since 2004, was declared. Officials said 40 people were evacuated from an apartment building after a tree smashed part of the roof.