Metro Washington's 300,000 white-collar workers have two chances--slim and none--of getting their regular October pay raise on time this year.

If the White House has its way, 1983 will be the year without a raise for the nation's 1.4 million government clerks, scientists and computer specialists. This is despite an official pay report, still under wraps, that will indicate that Uncle Sam needs to boost salaries about 20 percent to keep up with wages paid by private firms.

The House Post Office-Civil Service Committee has recommended that U.S. workers get a 4 percent increase in October. But that proposal from the committee, which considers itself a friend of the work force, likely faces an uphill fight in the Budget Committee and then on the House floor itself.

The Senate Governmental Affairs Committee has tentatively agreed to stick with an earlier Senate-House budget compromise that would delay the raise due in October until January.

It will be some time after Labor Day--and after the president has made his no-pay-raise proposal--before Congress decides when it wants the next federal pay raise, which would also go to members of Congress.

Last year President Reagan rejected pay data supplied by the Bureau of Labor Statistics which, when interpreted by the experts, indicated that non-civil servants got about 18 percent more in their paychecks than federal employes doing essentially the same work. He recommended instead a 4 percent raise, which went into effect because Congress did not object.

Under the current pay law, the president can recommend an alternate raise. His recommendation goes into effect unless the Senate or House objects. If that happens--and the Supreme Court decision knocking down the so-called legislative veto may have changed that procedure--the full amount of the catchup-with-industry raise is supposed to go into effect.

Congress seems intent on giving U.S. workers a 4 percent raise.

Chances are the budget it finally approves will call for the raise to be effective in January. Then the question is whether that raise can be insulated in a budget the president will sign or, if vetoed, one that Congress will vote to override.

Each year about this time federal workers notice that their landlords and parking lot owners look at them with renewed interest. Tell them to hold off for a while. This year the question is not how much the raise will be, but will there be one?