Fall Equinox occurs this Saturday at 7:49 AM, and right on cue, temperatures will dip towards the below-average side of the line, at least temporarily.
Right now, high pressure aloft is keeping us nice and warm, but temperatures begin a steady decline on Friday as that high pressure system gives way to a low dropping out of Northern California.
The most noticeable change will be morning fog and low clouds. With good onshore flow associated with the low, the marine layer will make a good nightly push into the Valley, beginning on Sunday morning. The burn-off should be quick each morning, and we can expect mostly sunny skies with perhaps a few high clouds here and there.
The temperature slide should bottom out on Monday, with highs only expected to reach 80, below the 83-degree historical average. Long-term, temperatures are expected to stay below normal through the end of the forecast period.
This certainly doesn't mean that summer heat is leaving for good. I would expect one or two more periods of heat this year before it gives way to our more mild winter pattern.
The good news for weather enthusiasts like myself is that October is normally when weather starts getting more interesting in the Los Angeles area. Santa Ana winds are notorious in the month of October and El Niño is expected to make an appearance in the coming weeks.