Civil servants won't know for months whether their 1988 pay raise will be 2 percent or 3 percent.

The difference for the average federal worker is relatively small: $540 a year for a 2 percent raise or $810 if it is 3 percent. But that extra 1 percent would do wonders for the local economy, which is based on the steady paychecks of the nearly 400,000 federal employes in the Washington and Baltimore areas.

President Reagan has proposed a 2 percent raise costing $1.5 billion. But there is growing pressure in Congress to tuck a slightly higher raise into the continuing resolution that must be approved to keep the government operating beyond the fiscal year, which ends Sept. 30.

In the next few weeks, Congress is expected to approve a temporary continuing resolution, to run the government through Nov. 20. Then it will begin work on a second resolution to finance federal operations through the remainder of the 1988 fiscal year. Rep. Steny H. Hoyer (D-Md.) plans to put in language authorizing a 3 percent raise in that second resolution.

Virtually the same thing happened last year. Reagan proposed 2 percent and Congress raised it to 3 percent. Retirement Handbooks

Government Retirement Benefits Inc. has published updated versions of its two handbooks on the old and new federal pension programs. Each gives a rundown on the basics of the plan, showing how to calculate benefits.

The 91-page handbook on the old plan, which covers all pre-1984 federal hires, is called "Your Civil Service Retirement System." Copies are $4.50.

The 128-page handbook on the new pension plan, which covers most new hires, is called "Your Federal Employees' Retirement System." Single copies are $5. For information, write GRB at 5400 Eisenhower Ave., Alexandria, Va. 22304, or call 461-9100 weekdays. Meetings

Classification and Compensation Society's Capitol Chapter will have its Friday luncheon meeting at the Stouffer Concourse Hotel in Arlington. Charles Goodsell, director of the Center for Public Administration and Policy at VPI, is the speaker. For information, call 783-4847.

Office of Management and Budget's Gerald Riso will speak at Friday's luncheon of the American Society for Public Administration's National Capital chapter. The session is at George Washington University's Marvin Center. Call 393-0428.

AFL-CIO President Lane Kirkland will address Wednesday's convention of AFL-CIO's Public Employees Department at the Capitol Hill Hyatt Regency. SES Pay Pitch

A line was garbled in Friday's column about the proposal to raise starting pay for people in the first two pay levels of the Senior Executive Service. It made it appear that 1,000 members of the Senior Executives Association would get the raises. However, most of SEA's 2,200 members are in higher pay steps in the executive service and would not get the raises.

Under the proposal, SES Level 1 would be raised $5,900 to $64,700, and Level 2 personnel would get increases of $8,800, raising their annual pay to $73,500.