Brief critical fire weather conditions returned to the Southland’s coastal mountain slopes today, with more warm, dry weather expected Thursday before a sharp change to the first truly cold days of autumn.

“Big swings in the weather this week, going from near normal temps, to much above normal, to well below normal all in the span of about four days,” the National Weather Service predicted.

Temperatures are expected to rise to 88 degrees on Thursday in Long Beach, according to the National Weather Service, then dip into the low 60s Saturday and Sunday.

Winds were expected to pick up Wednesday night across L.A. and Ventura counties, though below advisory level, the weather service said. Gusty west to northwest winds are expected starting Friday and lasting off and on through the weekend, with 35- to 55-mph gusts possible Friday night into Saturday.

The brief combination of heat, wind and low relative humidity—8-15%—will increase fire danger, prompting the NWS to warn residents to use extreme caution with potential fire sources. The NWS also warned residents never to leave children, seniors and pets in cars parked in hot weather as vehicle interiors can quickly become hot enough to kill.

The weather service also warned of dangerous sea and surf conditions, with gales of 30-40 knots and 10-20 foot steep seas.

A sharp cooling trend will arrive on Friday and continue into the weekend with a roughly 50% chance of rain or showers. Forecasters said the mountains and eastern L.A. County have the best chances for rain.

The NWS said “a very cold upper low will drop south along the West Coast Friday and usher in a much colder air mass that will stick around for the next several days.”