Virginia's unemployment rate fell nearly half a point in July from the previous month, to 3.8 percent, the Virginia Employment Commission reported yesterday.

Despite the large decline, officials said seasonal factors explained nearly all of the change and that the state's economy did not appear to be growing any faster.

Among the seasonal factors were students seeking work who either managed to find it or stopped looking, thereby removing themselves from the unemployment rolls. And employers typically add jobs for the summer, boosting payrolls in such industries as insurance and tourism for the season.

Seasonal factors also helped explain the drop in joblessness in Northern Virginia, to 1.9 percent in July from 2.3 percent in June. That rate was the lowest for any region in the state -- the next-lowest, Roanoke, was considerably higher at 3.1 percent and the comparable U.S. rate was 5.5 percent -- but signs of stagnation in Northern Virginia have not dissipated, according to Employment Commission research economist William Mezger.

Total payroll employment in the Northern Virginia area, for instance, rose only 0.3 percent, to 787,400, between July 1989 and July 1990. Construction employment fell 8,900 in the same period.

"Things are not as strong as they were at this time last year," Mezger said.