Rare August rainfall possible in SoCal. How Hilary will impact SoCal's weather

Rare August rain is possible in Southern California this weekend as Hurricane Hilary churns north off the Baja California Peninsula.

Hilary became a Category 4 hurricane by Friday morning as it moved up Mexico's Pacific coast toward California.

Hurricane Hilary

1-5 Rainfall forecast

Valid Aug. 17, 11 p.m. through Aug. 23, 5 a.m.
Source: NOAA

The hurricane was expected to take a more northward turn toward the U.S. border. The storm will then lose strength as it gets closer to Southern California with wind speeds decreasing from 120 mph early Saturday to 70 mph Sunday night and 40 mph by Monday evening.

"We're tracking what could be the remnants of a tropical storm that could bring some rain, especially Sunday into Monday," said NBC4 forecaster Belen De Leon. "It's going to become a major hurricane, but as it approaches the southwestern part of the United States it's going to weaken into a tropical storm. The winds are not going to be as strong, but it's still going to pack a punch."

Here's what to expect this weekend and into Monday.

When to expect rain from Hilary

The system will produce tropical moisture for Southern California Saturday through Tuesday. The region can expect moderate to heavy rain with the most significant rainfall likely Sunday through Monday.

Most of the area will be under a flood watch Saturday through Monday night. A rare tropical storm warning is in effect through Monday.

"On the forecast track, a turn toward the northwest and north- northwest is expected (Friday) and tonight, followed by a faster motion toward the north Saturday night and Sunday," the National Hurricane Center's Friday morning advisory said. "The center of Hilary will move close to the west coast of the Baja California Peninsula over the weekend and reach Southern California by Sun night. Fluctuations in intensity are likely over the next day or so. Weakening is expected to begin by Saturday, but Hilary will still be a hurricane when it approaches the west coast of the Baja California peninsula Saturday night and Sunday. Hilary is expected to weaken to a tropical storm by Sun afternoon before it reaches southern California."

Flooding, gusty winds and high surf are possible, but the storm's track will determine the severity and timing of severe weather.

"There's a possibility for several inches of rain in Southern California," De Leon said.

Even trace amounts of rain would be a rarity for Los Angeles in August, historically the area's driest month of the year. Early rain estimates are 1 to 2 inches throughout SoCal.

No tropical storm has made landfall in Southern California since Sept. 25, 1939, according to the National Weather Service, but that doesn't mean the region hasn't felt their influence. The hurricane center said Hilary could possibly survive briefly as a tropical storm and cross the U.S. border.

Unlike scattered showers earlier this month in parts of Southern California, the upcoming round of rain will likely be more widespread and heavy at times.

"Rainfall impacts from Hilary within the Southwestern United States are expected to peak this weekend into Monday," the National Hurricane Center said in a report. "Flash, urban, and arroyo flooding is possible with the potential for significant impacts."

Other affected area include a swath communities between San Diego and Yuma, Arizona, and the area from Bakersfield to Tucson, Arizona could also see rain.

The San Bernardino County Fire Department warned of the flood risk in recent wildfire burn areas.

"Flooding is possible throughout the county with an increased risk for residents near the El Dorado Fire and Apple Fire burn scars," the department tweeted. "Get prepared. Sandbags are available now."