Californian here and fire lookout. So although no official cause has been made I will give my best educated guess based on my knowledge of the region and knowledge of wildfires.

So normally we get some small amount of moisture during the late fall/winter months but it has been bone dry since May 2024. Since the drought came on the heels of huge wet season you have a lot of shrubs, grasses and dead chaparral(fuel) all over the mountain regions. Now we are coming into the new year and a massive atmospheric pressure system has built up over the desert regions that then force air through the canyon areas and into the Los Angeles basin(oxygen). These are called Santa Ana winds and are usually very intense however because of the earth being at 1.5C above pre-industrial levels those intense winds became hurricane force winds very quickly, we are talking 80-100mph. With all of these elements at play all that was needed was an ignition. Now that can be anything from a car backfiring, rocks colliding with each other and sparking to mylar ballon’s from birthday parties reflecting enough direct sunlight to ignite a leaf. Once that ignition source was created the fire had everything it needed to quickly go from a small flame to a massive wildfire.

With all these factors at play it was only a matter of time before a wildfire started. 4 fires is extremely abnormal however so are 80-100 mph Santa Ana winds and these longer dry seasons. I was born and have grown up and lived in this region for 30+ years, only once did I see a Santa Ana wind event that was as intense as it was Tuesday night however it has been getting hotter and dryer in Los Angeles for as long as I have lived here and it was only a matter of time before something like this hit. We were as prepared as we could have been for this and it still was not enough.

Also it’s not over yet, high winds are expected to pick up Thursday night-Friday morning and the fires are still not contained.

There are two different parts to that:

1. What was the ignition source, which is currently unknown
2. What caused it to go from a tiny fire to a huge fire very quickly, which is the result of having a couple of fairly wet years, followed by a very dry year, combined with hot dry winds. A warming world is in part responsible for those conditions.