Gasoline prices have spiked almost every year around this time. There’s a simple reason for it: U.S. refineries typically experience a capacity crunch around April every year because this is the time of year when they transition from winter to summer fuel blends.
California has what's called "boutique blends" of gasoline, where different regions of the state have different gasoline formulas.
The impact of this is that it takes California out of the national market for commodity gasolines, which increases the cost and the price of gasoline to Californians.
-PJ