Diesel prices continued to fall on Monday, Sept. 19, but with oil on the rise and another storm headed toward the Gulf of Mexico , it’s anybody’s guess how long that trend will last.

ProMiles reported a national average of $2.757 per gallon for diesel Monday, that’s down significantly from the post-Hurricane Katrina high of $2.89 per gallon reported by the U.S. Department of Energy. Some areas, including California , Idaho , Utah and Washington state, were still reporting prices of more than $3 a gallon.

Meanwhile, crude oil prices jumped more than $3.50 per barrel in trading on the New York Mercantile Exchange on Monday, sparked by fears over Tropical Storm Rita heading toward the Gulf of Mexico . Prices went as high as $66.60 per barrel in midday trading.

CNN reported that Chevron Corp. was already evacuating workers stationed on offshore oil and natural gas platforms in the Gulf in anticipation of Rita, and other companies were sure to follow suit. Forecasters predict the storm could increase to hurricane strength and hit the Texas and Louisiana coasts later this week.

The Organization of Petroleum Exporting Countries was meeting on Monday to decide whether or not to raise crude oil output to help stem worldwide oil price spikes, but news reports said ministers did not appear to be in favor of a raise.