NEW YORK (MarketWatch) — Gas prices are under $3 somewhere in more than half of the 50 states right now.

True, it may be hard to find that station, unless you live in Mississippi, where 30% of stations are selling regular unleaded that cheap, or four other states where more than one in five are doing the same, according to AAA. Overall, prices in just 4% of stations across the country are that low, it said.

And while 28 states have at least one station selling gas for less than $3, the national average is $3.34, according to AAA. A year ago, when the average price was about 14 cents higher, just 15 states had at least one station selling gas for under $3, and only 0.3% of stations nationally did, it added.

The states with the lowest gas prices are in the Southeast and in the center of the country, from the Great Lakes down to Texas, said AAA spokesman Michael Greene. These states are benefiting from the crude coming from Canada, the Bakken formation in North Dakota and Montana, and Texas or proximity to refineries that are running at record levels.

“Access to cheaper oil and abundant gasoline supplies can often trump the differences in gas taxes, especially in a state like New Jersey,” which has lower-than-average taxes but is in the high-demand Northeast, Greene said.

The cheapest gas is likely to be found at a station tied to a supermarket or convenience store, which hope to get consumers to also buy higher-margin items; an unbranded cash-only station; or a large truck-stop-style location that relies on high volume to offset low margins, according to Greene.

Of course, prices can vary dramatically within a few miles in the same town. A gas station attached to a Meijer supermarket in West Lafayette, Ind., was selling gas for $2.759 on Monday. A few blocks away, an Admiral station priced regular unleaded at $2.699, according to Gasbuddy.com, while a BP gas station a bit further down the road was selling gas at $3.119.

The average price across Indiana on Monday was $3.28, according to Gasbuddy. The cheapest place, on average, to buy gas was Springfield, Mo., at $2.988. The most expensive states for gas included New York, Massachusetts and those on the West Coast, it said.

Gas prices are likely to keep falling until later this year, AAA’s Greene said. The federation of motor clubs has forecast that the nationwide average could drop to between $3 and $3.10 by mid-December, the lowest national average since 2010.

These states on Monday had the highest percentage of gas stations with gas priced at $3 a gallon or less, according to AAA: