Pump prices are tumbling on the West Coast and averages for Oregon, California and Washington have all dropped below $4 a gallon, though that's still 50 cents higher than the national average, AAA Oregon reported Tuesday.

The national average for regular unleaded loses 4.5 cents to $3.50 and is at the lowest level since early February. Oregon?s average plunges 17 cents to $3.93 and drops below $4 a gallon for the first time since March 19th.

This is the second week in a row that Oregon has seen double-digit decreases. Last week?s decline was 13 cents.

The national average reached its year-to-date peak of $3.94 on April 6, and has fallen for 62 of the 64 days since.

Oregon?s average peaked for the year so far on June 1 at $4.27 a gallon, just shy of the record high of $4.29 set on July 3, 2008.

"Gas prices on the West Coast can be volatile because of this region?s tight refining capacity and its isolation from the rest of the country?s fuel sources," said AAA spokeswoman Marie Dodds.

Drivers in all states within the continental U.S. are now paying less than $4 per gallon on average for gasoline. Outside of Hawaii ($4.40) and Alaska ($4.29), California currently has the highest state average retail gasoline price at $3.98. Drivers in South Carolina pay the least, with a state average of $3.08 per gallon.

Lower crude oil prices and economic concerns both at home and abroad remain the primary reasons for the steady decline in retail gasoline prices. Crude oil was trading around $84 per barrel Tuesday, compared to $83 a week ago. For the month, crude prices are down about 10 percent.