The National Weather Service says Southern California will experience a moderate El Nino this fall and winter, a change that's likely to produce above average rainfall. On average, moderate El Ninos produce about 17 inches of rain in San Diego, which is five inches above the seasonal average. But the impact of the natural and periodic climate change can vary greatly. The last moderate El Nino occurred in 2003, when San Diego recorded 10.6'' of rain. In 2005, there was a weak El Nino, and San Diego recorded 22.5 inches of rain.
Forecasters worry about El Nino, in part, because the phenomenon can produce stronger and more frequent Santa Ana winds. The Santa Anas usually don't hit San Diego County as hard as they do Orange County. But San Diego has been whipped hard by the Santa Anas, which have in turn spread many wildfires. The scenario is of special concern this year, says the weather service, because inland San Diego County is drier than normal. The Santa Anas typically hit the county's mid-section, from Vista and San Carlos down to the Campo area.
In addition to producing more rain and wind, an El Nino can also result in below average air temperatures during the fall and winter.