The unemployment rate in the District fell almost a full point from November's 10.9 percent to 10 percent in December, the D.C. Department of Employment Services said yesterday.

The department also reported a slight decline in unemployment in suburban jurisdictions, where the rate fell from 5.7 percent in November to 5.4 percent in December.

Despite declines that have been reported in recent months, officials cautioned against describing the development as a trend because activity reported since the beginning of 1982 has been irregular.

At the same time, the same officials noted, there apparently is no single identifiable factor that accounts for the decline in December, although seasonal hiring accounted for a substantial part of the increase.

Despite a significant decrease in the number of government jobs in recent months, 55 percent of the increase in December was attributed to seasonal hiring in both federal and local government sectors.

In the District, the labor force appeared to have declined between November and December. The number of jobless workers in the District in December declined from 35,200 to 31,900. DES officials noted, however, that employment remained relatively constant, dropping by 200--from 286,800 to 286,600.

The number of unemployed workers in the metropolitan area declined by 6,700 between November and December.

A comparison of seasonally adjusted estimates for December 1981 and December 1982 shows that the number of jobs in the District decreased over the year, from 610,100 to 608,500. Over the same period, the number of jobs in metropolitan Washington increased from 1.59 million to 1.6 million.