Despite being in the midst of what should be considered San Diego's dry season, showers drenched San Diego County Friday morning.

The region's dry season typically begins around April 1 but a weak El Niño is bringing rain well into the spring, according to the National Oceanic and Atmospheric Administration (NOAA).

On Friday, heavy showers were creating slick roadways across the county. Light showers and a chance for thunderstorms were expected to continue throughout the day and into Saturday, NBC 7 Meteorologist Sheena Parveen said.

The heaviest rain is expected Saturday morning with the best chance of thunderstorms Saturday afternoon.

Parveen said the "mess of a weather system" bringing rain to the region is not following any standard pattern. But it will begin to break apart by Mother's Day.

NOAA said the reason for this year's unusual rainfall pattern is that San Diego is in the midst of a weak El Niño pattern.

An El Niño develops when the Pacific Ocean water temperature rises .9 degrees Fahrenheit for three consecutive months, causing atmospheric conditions and rainfall patterns to shift.

Typically across the southern United States, that means more rain during the winter.

But in San Diego, it means an unusual rainy season that could stretch through early fall with several chances of measurable precipitation if Pacific Ocean water temperatures remain above average, NOAA said.

The last time San Diego experienced a strong El Niño was in 1998 when rainfall averaged at 188% above normal.

Twenty-four-hour rainfall totals as of 7:15 p.m. Thursday were low across the county. Only Del Mar, Carlsbad, and Fashion Valley saw more than a tenth of an inch.

Midcap said the rain would continue through Sunday, with the heaviest and most unstable coming on Saturday.

The coast, valleys and mountains could see between a half-inch and an inch-and-a-half of rain by the end of the weekend.

The National Weather Service urged drivers to use caution on the road during this weather period but no watches or warnings were in effect as of Thursday.