U.S. gasoline prices were $4 per gallon again on Monday as the U.S. and Iran traded strikes through the weekend. 

The average national gasoline price was $4.003 per gallon, according to AAA.

Indiana had the cheapest average gas price, at $3.35, while California drivers were paying the most, at $5.50 per gallon. Even Hawaii, which sees high gas prices due to its remote location, had lower gas prices than California, at $5.42 per gallon. 

The West Texas Intermediate oil price, the American benchmark, was at nearly $82 per barrel on Monday, up from $68.50 at the start of July when an interim peace agreement was signed between the U.S. and Iran. That agreement, intended to provide a ceasefire while a more lasting peace deal was negotiated, has since crumbled as hostilities have resumed.