CAISO predicted demand of 762657 Mw and assumed DUKE would be online. Instead, demand hit 792746 and DUKE had 30000 offline. As a result, there was a shortage of 60089Mw, and spot prices hit $152.
Today CAISO adjusts demand, and factors in DUKE being offline and orders 786722 Mws. Today's spot price is at $32. So far, it looks like actual demand is exceeding forecast by 15221 Mw (subject to a lot of revisions) but that is easily within the usual range.
Last time Spot price shot up over $100 was on May 28th when CAISO got caught with their pants down and missed demand by 39399 Mw, the highest number I've recorded so far.
It's not enough to be hot, it has to be unexpectedly hot AND/OR something has to break.