Retail sales dropped 0.5 percent in the week ending Saturday, as unseasonably warm temperatures hit most of the country, a U.S. trade group said. The International Council of Shopping Centers said warm weather continued to dictate the flow of the retail industry. Unseasonably warm weather has pushed shoppers into early spring shopping recently. \"Record-setting warmth held its ground across the East last week with the warmest fourth week of March in 20 years,\" Weather Trends International said. The exception for the week was the great Northwest, where temperatures were the third coldest for the week in 20 years \"and the snowiest,\" ICSC said, as a late snowstorm covered the region. Sales overall dropped compared to the previous week, but posted a gain of 2.7 percent compared to the same week of 2011. The trade group said the average national price of gasoline rose by 5.1 cents to $3.918 per gallon Monday compared to the previous week. The average price of gasoline is the highest it has been since May 2011. The average price at the pump is up 66 cents since late December, the U.S. Energy Information Administration said.