Powerful Santa Ana winds, with gusts reaching hurricane strength, swept down the mountains outside Los Angeles and spread wildfires into several neighborhoods starting Jan.

By the time the winds get to the point where the Eaton Fire broke out in Altadena on Jan. 7, it’s not uncommon for them to have less than 5 percent relative humidity, meaning essentially no moisture at all.

High-speed winds this week have the potential to knock over semitrucks and cause other hazardous driving situations. Here's what to know.

A damaging Santa Ana wind event was peaking early Wednesday and was expected to stay strong through early afternoon.