Updated May 26, 4 p.m. EST

Planning to hit the road this summer? You might want to keep an eye on the AAA Fuel Gauge Report, which takes the daily temperature of gas prices around the nation.

The national average on May 26 for regular gas was $3.81 a gallon -- up $1.04 from a year ago. That's a 38% increase. Thankfully, gas prices have come down slightly in time for Memorial Day weekend, but some traders are betting that they'll rise again soon.

Gasoline futures are higher this week on the expectation that refinery outages in Illinois will cut into supply. Demand for fuel is likely to rise over the weekend as Americans hit the road.

As gas prices have soared this year, some experts wonder whether gas prices could reach $6 a gallon. Ridiculous? Not when you think about the perfect storm of factors pushing pump prices ever higher.

Speculators: A growing number of experts now think the gasoline market is being distorted by traders and investors who are speculating, Maclean's reports. "You simply can't explain these levels of volatility by supply and demand because market fundamentals don't shift that quickly over such a short period of time," a law professor and former commodity futures regulator told the magazine. "Most observers now believe speculators are actively manipulating oil prices."

Libya: The U.S. doesn't even get much oil from Libya; most of Libya's light sweet crude goes to Europe. But the U.S. imports 40% of its crude from Europe, refines it and sends it back to Europe in the form of gasoline and diesel, ABC News reports.

So if Europe feels the hit from Libya, the U.S. will, too. Global oil output fell in March to 88.3 million barrels a day, a 700,000-barrel drop mainly due to reduced supply from Libya, MarketWatch reports. Experts are watching closely to see whether the unrest in the Middle East will spread to Saudi Arabia, which supplies 11% of America's crude oil, according to ABC News.

The falling dollar: The dollar is depreciating as investors realize the U.S. is not the place to find high interest rates on their money. They're going elsewhere for higher rates, causing the dollar to fall.

That means $1 won't buy as much gas as in the past (not that $1 ever bought much gas in recent memory). Commodities are priced in dollars, CNBC reports, and are coming at a discount on the foreign markets.

Rising demand: Economies across the globe are climbing out of recession, putting people back to work. They need more gas to get there, so demand is growing in strengthening economies.

All of those factors have led one economist, Richard Hastings at Global Hunter Securities in North Carolina, to think that $6 a gallon for gas is a real possibility. All you need now are a couple of damaging hurricanes in the wrong place, he told CNBC, and "prices could go up in a quasi-exponential manner."

Hastings said that in that case, gas would have no problem reaching $6.50 a gallon this summer.

We're already seeing people make changes in response to the uptick in gas prices. ABC News reports that in some cities, total strangers are meeting up to share a ride and hop into the carpool lane. Other people are showing new interest in hybrid or electric cars like the new Nissan Leaf.