The National Weather Service issued a statement Wednesday warning residents of Los Angeles and Ventura counties to expect cold and windy weather with scattered showers Thursday and Friday.

A cold, low-pressure weather system is combining with so-called "king" tides to increase flood danger along the California coast, forecasters said.

Daytime highs in the upper 40 s and low 50 s in most coastal and valley locations will be followed by sub-freezing overnight temperatures through the weekend. Wind gusts could reach 25 mph Thursday.

Normal average temperatures in the Los Angeles area for January are highs in the 60 s, with lows in the mid-40 s for coastal areas and low 40 s in valleys, according to Joe Sirard, an NWS meteorologist.

"We're looking at temperatures dropping to at least 10 degrees below normal," Sirard said.

Top temperatures Wednesday in Los Angeles and coastal areas were in the high 60 s and lower 70 s. Temperatures are expected to drop to highs in the mid-to-upper 50s Thursday before plummeting to the upper 30 s or mid-40 s overnight into Friday.

In Long Beach, the temperature will drop from a high of 68 on Wednesday to 56 Thursday before plummeting to 39 overnight into Friday.

The San Fernando Valley will be slightly colder Thursday, with highs in the upper 40 s to mid-50 s and lows in the upper 20 s and mid-30 s. Highs Friday are forecast in the mid-50 s.

In the San Gabriel Valley, highs in the mid-50s Thursday will give way to a low of around 40 Thursday night. Friday will have highs in the upper 40 s to mid-50 s.

The coldest temperatures are expected Saturday morning as winds let up. Coastal valley low temperatures are predicted in the mid-20 s in some areas, with a potential six hours of subfreezing weather threatening crops and garden plants. The NWS warned farmers and anyone with sensitive plants to prepare for "several nights" of potentially sub-freezing conditions.

Coastal temperatures on Saturday morning should dip into the low to mid-30 s, with single-digit temperatures in some Antelope Valley spots.

Extreme cold and "dangerously low wind chills at times" are predicted for Southern California mountains, where icy roads and possible "black ice" will make driving extremely hazardous. Mountain highs are expected in the 20 s and 30 s.

The wind chill factor could be as low as 10 below zero in the mountains Thursday night into Friday morning and in the teens down to the single digits for interior valleys and the Antelope Valley.

There will be only slight improvement in temperatures overnight Sunday - two degrees at most. A slight warming trend is forecast early next week, with normal temperatures returning midweek.

Rainfall totals are expected to be light - a tenth of an inch or less in most areas.

The NWS reports that snow levels are expected to drop rapidly Thursday, starting at 5,000 to 6,000 feet in the morning and dipping to 3,000 feet by the early afternoon. Snow levels could drop further into Thursday evening and Friday morning.

Less than 3 inches of snow is expected from the impending storm.

A coastal flood advisory for Los Angeles County beaches will be in effect from 5 a.m. Thursday through 11 a.m. Saturday, the NWS reported. High surf and windy conditions are expected to batter the coastline, with flooding more likely on low-lying beaches and beach parking lots. Beach erosion could occur in some areas.

The coastal flooding is expected to be worse due to astronomical conditions. "King" tides and the low-pressure weather system make for an increased flooding risk, the NWS said.

Strong onshore winds and the position of the sun and moon relative to the earth will combine to boost the chance of flooding at local beaches.

"It may reach into some of the local streets," said NWS meteorologist Stuart Seto.

The flood danger on the coast is predicted to be the worst beginning Thursday morning and continuing through Saturday, with high tides about 7:20 a.m. Thursday at 6.9 feet, 8:10 a.m. Friday at 7 feet and 9 a.m. Saturday at 6.8 feet, according to an NWS coastal-hazard message.

The extreme winter weather is being brought to Southern California by a very cold low-pressure system traveling in from the north early Thursday. Besides cold temperatures and scattered showers, strong winds out of the north will make it feel even colder.

eric.bradley@presstelegram.com, 562-499-1254, twitter.com/EricBradleyPT