Voters in Virginia, Maryland and the District of Columbia are expected to turn out in average numbers today, despite cloudy skies, scattered showers and gloomy feelings about the 1980 presidential election.

Citing a flood of absentee ballot applications in Maryland and a last-minute surge in voter registration, especially in the Virginia suburbs, election officials predicted a turnout in the Washington area roughly equal to that of 1976 and, as usual, far greater than the nation's.

Virginia's election chief predicts a 78 percent turnout, compared with official predictions of a 72.5 percent turnout in Maryland and 60 percent in the District. Nationwide turnout is expected to be about 50 percent, but officials caution that the figures cannot be contrasted directly since they are calculated against different bases.

Polls will be open in the District and Maryland from 7 a.m. until 8 p.m. In Virginia, the hours run from 6 a.m. to 7 p.m.

While the turnout appears somewhat predictable, Carter and Reagan supporters acknowledged that the presidential contest in Maryland and Virginia could still hold surprises, largely because of the unknown impact of escalating hopes for a resolution of the Iran crisis. Last-minute shifts at the top of the ticket also could spill over into three close congressional races in the Virginia and Maryland suburbs.

As of the weekend, President Carter appeared likely to win 13 electoral votes and D.C.'s three -- compared with 12 for Ronald Reagan in Virginia, where the Republican had a comfortable 10-point margin in recent polls.

Turnout was expected to be a factor in Maryland, where Reagan supporters insist their candidate is in striking distance, despite the state's three-to-one majority of registered Democrats over Republicans.The Carter forcers were hoping for heavy voting in the Democratic stronghold of Baltimore City to counter Reagan's perceived strength in western Maryland and the Washington and Baltimore suburbs.

The election will test the impact of a last-minute surge in voter registration in early October. Maryland's rolls broke the 2 million mark for the first time, an increase of 115,000 since 1976. Despite the increase, the ratio of Democrats to Republicans held at three to one. In Virginia, the rolls swelled 200,000 to 2.3 million, with the biggest gains in traditionally Republican areas.

Maryland election chief Willard Morris cautioned that tens of thousands of voters may be on the rolls more than once, in different counties, since there was not time to cross-check the unprecedented number of last-minute registrants against all the county voters' lists. The same problem could occur in Virginia and the District, where registration also surged during the final days.

It is a felony, under state and federal laws, for a person to vote more than once, officials warned. In the District, U.S. Attorney Charles F. C. Ruff announced that his office has established a hot line -- 628-6011 -- to take reports between 7 a.m. and 10 p.m. today of suspected election irregularities in Washington.

At stake in Virginia today will be the fates of the states' two liberal Democratic congressmen, Joseph L. Fisher in the 10th District and Herbert E. Harris in the 8th. Both men, who represent the Northern Virginia suburbs, are locked in close races with Republican opponents who hope to ride to victory on Reagan's coattails and conservative shifts in the districts.

Fisher faces Republican Frank Wolf and Harris faces former congressman Stanford Parris, whom he unseated in 1974. The Democrats are banking on widespread ticket splitting to keep them in office even if Reagan sweeps their districts.

In Maryland, Republican Rep. Robert Bauman, considered one of the surest winners until a month ago, is an underdog to challenger Roy Dyson, a Democratic state delegate, because of reaction in the sprawling, conservative district to Bauman's recent admission to the "twin compulsions" of homosexual tendencies and alcoholism.

Another Maryland incumbent who seemed vulnerable, Prince George's County congresswoman Gladys Noon Spellman, was stricken with a massive heart arrest Friday, with her prospects for recovery unclear. She is still a favorite to defeat Republican challenger Kevin Igoe.

In Montgomery County, incumbent Congressman Michael Barnes is fighting off a challenge from former Rep. Newton Steers, the Republican he unseated two years ago. Barnes had pulled ahead by five percentage points or more in most polls by last weekend.

Maryland's Republican Sen. Charles McC. Mathias appears headed for an easy reelection victory, despite a determined challenge from hard-running Democrat Edward T. Conroy, a Bowie state senator.

Voters in the two states also will choose a number of local officials and voice their opinion on a variety of referendums on subjects as diverse as the composition of the Prince George's County Council and Reston's status as an unincorporated area. In Montgomery and Prince George's counties new school board members will be chosen, while in Arlington one seat on the County Board is at stake.

In the District, voters have been preoccupied with an initiative that could start the federal city along the somewhat uncertain route to statehood and a second that, if passed, would legalize a city-run lottery and daily numbers game. Six City Council seats also are at stake, as is the seat of congressional Del. Walter Fauntroy, who is heavily favored to win reelection.