Unemployment in the District of Columbia dropped from 8.8 to 8.4 percent in October, but still remained considerably above the national rate and that for the Washington metropolitan area as a whole, the D.C. Department of Labor reported yesterday.

There were 27,500 Washingtonians of the city's 231,200-person available work force looking for jobs in October as compared to 28,800 the previous month. The October 1978 figure is a full percentage point below the 9.4 percent rate recorded in October 1977.

Despite the October decline, the city's unemployment rate was well above the 5.8 percent national unemployment rate recorded in the same month.

In the overall Washington metropolitan area, 70,100 of the 1,558,200 available workers -- 4.6 percent -- were out of work, a figure only 600 persons -- less than 0.1 percent -- below the September rate. In October, 1977, area unemployment stood at 4.9 percent.

The rates are adjusted to account for seasonal variations in employment.

The D.C. labor department's figures give no monthly indications of changes in unemployment among black youths, which on a national basis has hovered around 40 percent during the past year.

In June, it was reported that black youth unemployment in the District in 1977 was well above the national average -- 48.5 percent. A U.S. Labor Department spokesmen estimated yesterday that black youth unemployment here is still in the 25 to 50 percent range.

While the number of workers went up on both the city and areawide levels, there was also an increase in the number of persons in the labor force -- 3,600 more potential workers in the city and 13,600 areawide. At the same time, there was an increase in the number of available jobs, which rose by 4,700.

D.C. labor director Thomas A. Wilkins said 3,500 of those jobs were in government, mostly among local suburban jurisdictions. Jobs in District government decreased during the same period by 100.

Mild weather forstalled a usual decrease in construction jobs, Wilkins said. The largest increase came in the area of service jobs, which rose by 1,400, and wholesale and retail jobs, which went up by 1,200.

Government jobs decreased by 1,900 in the city, finance, insurance and real estate jobs by 400 and manufacturing employment by 100, Wilkins said.