Southern California braces as "major and long-lasting heat wave" approaches, NWS says

While much of the country gets its first taste of fall weather, the first half of October could be marred by a "major and long-lasting heat wave" across Southern California, according to the National Weather Service.

Forecasters say the extended period of heat could bring maximum temperatures 10 to 15 degrees above the average for this time of year. 

Because of the unusual heat that could bring along dangerous temperatures, CBS LA has issued a Next Weather Alert starting 4 p.m. Wednesday. Its end date remains unclear, and it could last for as long as two weeks.

"This is not going to be a one or two-day heat event," said CBS LA Chief Meteorologist Paul Deanno. "Starting Friday, it's going to get home and it's likely going to stay hot for a while."

The NWS noted that humidities are likely to be lower than previous heat events in September and August, meaning October's prolonged heat will be mostly dry. Past history suggests, according to Deanno, that rain chances won't ramp up in the region until November.

"It's not time for rain ... yet," Deanno said. 

Computer models remain split as of Wednesday on the length of the heat event, with some forecasting 7-10 days of heat while others keeping it abnormally hot through Oct. 15. Confidence in heat models will rise as time passes, according to CBS LA meteorologists.

In the buildup to Friday, temperatures across the region are expected to rise 3 to 6 degrees above normal through Thursday.