Windy conditions Wednesday prompted a warning from the San Joaquin Valley Air Pollution Control District regarding potentially unhealthy concentrations of blowing dust, but mild rainfall a short while later seemed to clear up the atmosphere somewhat.

The warning was in effect until late Wednesday afternoon, but rainfall that had been expected later in the day hit Kern County about noon instead and lasted for about a half hour in downtown Bakersfield before dissipating.

Bakersfield got .02 inches of rain.

Officials said exposure to "particulate pollution" caused by blowing dust can cause serious health problems including aggravated lung disease, increased risk of respiratory infections, asthma attacks and bronchitis.

The Associated Press reported slick roads in northern California during the morning commute, and there were isolated power outages and flooding.

A more powerful storm is expected to arrive Friday and last through the weekend, with the possibility of some areas receiving as much as 18 inches of rain over a five-day period, and wind gusts as high as 70 mph.

The AP reported officials were also warning of potential mudslides in the Sacramento Valley.

Conditions in Kern County are expected to be relatively mild.

National Weather Service meteorologist Daniel Harty said at least two more systems will pass through the area by Sunday evening, but total rainfall is only expected to add up to about a quarter of an inch.

"It's always hard to pin down rainfall amounts, especially farther out, but a quarter of an inch seems reasonable," he said.

The systems will be fairly warm, with temperatures throughout the rest of the week staying in the high 60s.