U.S. new-car sales zoomed 73.1 percent over year-ago levels in mid-June, marking the best domestic sales performance for the period in five years.

Rebates and incentive programs, some of them featuring 8.8 percent financing rates on selected models, contributed to the improvement.

Also, cars usually sell better in the spring and summer--and the national sales figures now include cars manufactured by Honda in Marysville, Ohio.

But a lot of the boost came from renewed consumer confidence, much of which is manifesting itself in the Washington metropolitan area, according to local dealers and dealer representatives.

For example, according to figures released yesterday by the Automotive Trade Association-National Capital Area, local dealers sold 34,144 cars in the first three months of 1983.

That is a 17.6 percent increase over the 29,037 cars sold by area dealers in the same period last year.

Imports accounted for 40.5 percent of local car sales in the first quarter, up from 38 percent for the year-ago period.

"We believe the next quarter will be even better," People are getting interested. Things really are beginning to come alive," said Gerard N. Murphy, executive vice president of the trade association.

Murphy said he doesn't believe the increase in sales is a fluke. "Things may slow down a little in the fall, but we're not pessimistic," he said. "Overall, you're going to see a good year."

Nationally, automakers said they sold 205,444 cars in the June 11-20 period, up 73.1 percent from 118,695 sold in the same period last year. The daily selling rate for the period was 25,680, the best since 28,188 cars were sold each day in mid-June 1979.

General Motors Corp., Ford Motor Co. and Chrysler Corp., all of which had sales-incentive programs during the period, showed mid-June increases above 60 percent.

Specifically, GM was up 77.6 percent, from 68,498 to 121,629; Ford Motor Co. sales improved 60.8 percent, from 30,781 to 49,502; and Chrysler Corp. posted a 77.1 percent gain, from 14,734 to 26,091. American Motors Corp. reported an estimated 78 percent increase, from 2,500 to 4,450.

Volkswagen of America Inc. posted a 2.9 percent gain, from 2,182 to 2,245. Honda of America Manufacturing Co. Inc. sold 1,527 cars. Honda began building cars in the United States this year.