Typically, the firefall only occurs in February at Yosemite when light from the setting sun hits the Horsetail Fall at just the right angle, turning it into what looks like a lava-spewing cascade. So, what happened this week was an incredibly rare site.
The Horsetail Fall had been running dry due to ongoing drought conditions up until an atmospheric river passed through the region on Sunday. San Francisco photographer, Scott Oller, captured the moment and noted that few fortunate photographers and tourists were able to alongside him. A much different experience than the crowded scene it typically brings in February.
You might be able to catch glimpses of it through Halloween weekend, but if you're looking for some extra notice check back in February.