Missouri became the first state Friday to have an average statewide gas price fall below $2 per gallon since 2009, while Oklahoma's average was expected to drop below that threshold sometime over the weekend, according to AAA.
The national average gas price was at $2.32 per gallon Friday, which AAA spokesman Michael Green said was the lowest since May 2009. That average has dropped for 92 days in a row, he said, which is the longest streak since AAA started keeping daily records in January 2000.
Gas prices have fallen every day since Sept. 25, for a total of $1.02 per gallon, Green said.
"The steady decline in gas prices this autumn is unlike anything we have previously tracked," he said.
Missouri's average on Friday morning was $1.98, according to AAA. Oklahoma had the second-lowest average at $2.01 and "is likely to drop below that price point this weekend," Green said.
Kansas had the third-lowest statewide average at $2.06 per gallon, while Texas and Indiana each averaged $2.09, Green said.
Gas prices are about 94 cents a gallon lower than they were a year ago, and AAA estimates consumers nationwide are saving more than $450 million per day on gasoline compared with the highs of spring and summer this year.
The slide is expected to continue in the short term.
"Consumers could ring in the New Year with gas prices about 5 to 10 cents per gallon less than today, which would make for the lowest New Year's gas prices since 2008," Green said.
A government report earlier this week said the economy has been benefiting from sinking energy prices, and that cheaper gas has freed up money for Americans to spend on other items, such as cars, clothes and appliances.
It's uncertain how long those prices will continue their descent before rising again due to typical season trends, Green said. Refinery maintenance and decreased refinery production could push prices upward within a month.
"Of course, if the slide in crude oil continues, then we may see gas prices drop even further," he said. "But at this point, no one knows when the oil market will reach a bottom."