"You are going to pay a little more than we thought you were going to pay," says Tom Kloza, chief oil analyst at the Oil Price Information Service and GasBuddy.com. "But you are not going to see any apocalyptic numbers."

Gasoline prices typically fall in the weeks following Memorial Day, after supplies increase enough to fill up the cars of the nation's vacationers as summer approaches. Prices have declined during the previous three Junes, by an average of 21 cents per gallon, according to AAA.

This year, drivers are paying more. The average has risen every day for a week, and is now higher than it was on Memorial Day — with more increases sure to come.

Higher fuel costs can reduce economic growth — in the U.S. and around the world — because they raise costs for businesses and leave drivers with less money to spend on other things.

In the U.S., a ten-cent rise in the price of gasoline only costs a typical driver an extra $1.50 to fill up a tank, but if that rise is sustained over a year it costs the U.S. economy $13.5 billion.

The average gas price so far this year, however, is still 5 cents cheaper than it was last year over the same period.

Even before violence in Iraq broke out, gasoline prices were falling more slowly than expected because of rising U.S. fuel demand and extensive maintenance at some Gulf Coast refineries that reduced gasoline output.

Then, last week, Iraqi insurgents seized a pair of cities and pledged to attack Baghdad. None of Iraq's oil fields were targeted — most are far away from the fighting — and oil exports have continued to flow. But Iraq is OPEC's second-largest exporter, so concern that oil production might be impacted has been enough to send global oil prices up by $6, to around $115 per barrel.

The average price of gas rose 3 cents per gallon during the past week, and analysts expect more increases over the next couple of weeks.

Higher crude prices generally make for higher fuel prices around the world, too, but the effects on drivers vary widely.

In many countries, gasoline prices are subsidized, so drivers don't see the effects of price changes quickly. In other nations, especially in Europe, fuels are taxed so heavily that a moderate change in the underlying price of fuel is hardly noticed.

How the situation in Iraq plays out is hard to predict, but analysts note that the global market is well-supplied with oil and fuels. Morgan Stanley wrote in a recent report that the potential for a significantly higher sustained oil price was "limited without a major disruption," and that "the conflict will likely be contained primarily North of Baghdad, limiting the impact on oil exports."

But drivers in 15 states are already paying more for gas than they have since March of 2013, according to Kloza. The national average will likely soon surpass this year's high of $3.70 per gallon, set on April 28.

Kloza thinks the national average may get close to last year's high of $3.79 per gallon, but he does not expect to see it reach the highs of 2011 and 2012, when it rose above $3.90 per gallon.

And the chances of the average crossing the $4 mark?

"The (last place) Mets have a better chance of winning the World Series," he said.