Retail food prices in the Washington metropolitan area rose 1.8 percent in February--almost double the average increase for all cities in the same month.

The increase followed the pattern set in January, when prices rose 1.6 percent and seemed to promise a return to the normal pattern of rising prices. Based on the two months of price increases, the annual rise would be 22.4 percent, according to the Bureau of Labor Statistics.

Last year, with prices held down for several months by supermarket price wars and other factors, prices here actually declined 0.2 percent from December 1980 to December 1981. The year before, prices had climbed 14.4 percent.

Chief culprits in the price increases reported yesterday were fruits and vegetables, particularly lettuce and tomatoes.

"While the price increase for lettuce and tomatoes for the nation was sizable, it was much greater in the Washington area," said Jesse Thomas, a BLS economist.

For instance, Thomas noted that the price of tomatoes increased 17 1/2 percent nationally and approximately 51 percent in this area, and lettuce prices climbed 28 percent here while falling 20 percent nationally. But Thomas said the differences might be just matters of timing, with the D.C. area a bit behind the national increases. He added that lettuce prices had climbed 49.9 percent nationally last month while rising 11 percent in the Washington area.

Egg prices also rose sharply in the Washington area, but price increases for eggs had been moderate the month before. Washington-area shoppers got a break on the prices of fish and seafood, poultry and frozen prepared food, all of which went down.

Figures on area grocery store food prices are released every month by the BLS. Area figures on the complete list of consumer goods and services--the consumer price index--are released every other month.