With the greenback coming under increased pressure from Federal Reserve policiesand investor appetite for more risk, there seems little direction but up for commodity prices, in particular energy and metals.

Weakness in the US currency feeds upward pressure on commodities, which are priced in dollars and thus come at a discount on the foreign markets.

One result has been a surge higher in gasoline prices to nearly $4 a gallon before the summer driving season even starts, a trend that economists say will be aggravated as demand increases and the summer storm season threatens to disrupt oil supplies.

"All we have to have is a couple badly placed hurricanes which could constrain some of the refinery output capacity in some key locations," says Richard Hastings, strategist at Global Hunter Securities in Charlotte, N.C. "If you get weakness in the dollar concurrent with the strong driving season concurrent with the impact of one or two hurricanes in the wrong place, prices could go up in a quasi-exponential manner."

Using a model that combines "subtle rates of change" with movements in the dollar index and commodity prices, Hastings figures the low dollar is responsible for about one-third, or $1.31, of the total gas-at-the-pump cost. Regular unleaded Wednesday was $3.84 a gallon nationwide, according to AAA.

While there's far from unanimity about the dollar's future course, the proportionate contribution that currency weakness makes to oil prices is clear.

The dollar as measured against a basket of foreign currencies has dropped 6 percent this year, while regular unleaded gasoline is up about 28 percent.

Gas prices also have been boosted from turmoil in the Middle Eastwhich in turn has triggered a wave of speculation that traders estimate has added about $15 or so to the cost of a barrel of crude , which is now teetering above the $110 mark.

Hastings sees gasoline having "no problem" getting to $6.50 a gallon over the summer after increased demand and storm disruptions come into play.

Others, though, say gasoline prices haven't needed any help so far from other events—the moves by the Fed to keep interest rates in negative real terms are enough to boost energy by themselves.

Michael Pento, senior economist at Euro Pacific Capital in New York, says there is an almost perfect negative correlation between the falling dollar and oil prices—minus-0.9 to be exact.

"When you have negative correlations that strong, it's not hard to understand that the reason why we're having this price spike in commodities is primarily because of the weaker currency and not because of shortages of oil or international tensions or global growth," Pento says.