Voters in Maryland, Virginia and the District of Columiba go to the polls today to elect a senator, several House members, a governor and scores of local officeholders including mayor of Washington.

In Virginia and Maryland, voters additionally will vote on a local ballot issues ranging from whether to egalize horse race betting in Virginia to whether to cut or limit property taxes in Montgomery and Prince George's counties in Maryland.

Polls will be open from 7 a.m. to 8 p.m. in Maryland and the Distrivct and from 6 a.m. to 7 p.m. in VIrginia.

The whether outlook for the day calls cloudy skies with a 40 percent chance of rain, according to the National Weather service. Temperatures should be in the low 60s during the day.

Topraces include the contest for U.S. senator in Virginia between Democrat Andrew P.Miller and Republican John W.Warner, for governor of Maryland between Republican J.Glenn Beall and Democrat Harry R. Hughes and for mayor of Washington between Democrat Marion Barry, Republican Arthur Fletcher, independent Glova Scott and U.S.Labor Party candidate Susan Pennington.

In addition, there are six races for U.S. House seats in the Washington area. In Northern Virginia, 8th District incumbent Democrat Herbert E. Harris IIfaces Republican John F. (Jack Herrity and independent Charles E.Coe. In the 10th District, Republican Frank R.WoIf is challenging incumbent Democrat Joseph L. Fisher.

In Maryland, there are three area House races-4th Districtincumbent Republican Marjorie S.holt against Democrat challenger Sue F. Ward, 5th District incumbent Democrat Gladys noon Spellman against Republican Saul J. Harris and 8th District incumbent Republican Newton I. Steers Jr. againstDemocrat Michael D.Barnes.

In the District of Columbia, Walter E. Fauntroy, the incumbent Democratic nonvoting delegate in the House, faces four opponents-Republican Jackson R. Champion, D.C. Statehood candidate Gregory A. Rowe, U.S. Labor Party candidate Cloid J. Green and Workers Party candidate Charelotte Reavis.

Both Montgomery and Prince Goerge's counties also have contests set for the position of county executive. In Prince George's, incumbent Democrat Winfield M. Kelly Jr. is opposed by Republican Lawrence J. Hogan, and in Montgomery, Democrat Charles W. Gilchrist faces Republican Richmond M. (Max) Keeney.

Suburban Maryland voters also have a variety of candidates for school board, county council and state legislative seats to elect.

At the statewide level in Maryland, there are additional contests for lieutenant governor, attorney general and comptroller.

In suburban Virginia, Arlingtonians will elect a new County Board member and a commissioner of revenue.

Two statewide ballot issues will be before all Virginia voters: whether to authorize pari-mutuel betting on horse racing and whether to allow tax exemptions for renovated or rehabilitated property.

Voters in Maryland will face 12 statewide ballot questions ranging from allowing salary changes for certain officeholders to modifying obsolete language in various provisions of the state constitution.

A number of county-level questions also will appear on the ballot in Montgomery and Prince George's counties.

In addition to the mayoral and House delegate races in the District of Columbia, voters will elect a new City Council chairman, two at-large council members and ward-level council members from ward 1, 3, 5 and 6.

D.C. voters will cast their ballots in one of three different waysdepending on which ward they live in.

In Ward 5, an experimental punch-card ballot system called Datavote will be used. The voter, using a special stylus, will pierce the ballot box adjacent to the candidates of his choice.

Voters in all the other sevens wards of the city will use traditional paper ballots. In wards 2 and 4, however, they will feed the ballots into automatic counting machines called Valtecs. In wards 1, 3, 6, 7 and 8, voters will dropballots into conventional ballot boxes for tabulation later at a central counting room downtown.

Close elections are possible in wards 5 and 6, where two candidates for City Council seats have organized write-in campaigns. In Ward 5, Robert Artisst, who lost narrowly to incumbent William Spaulding in September's Democratic primary, has circulated thousands of printed write-in stickers with his name on them. Patricia Rice Press, who lost to incumbent Council member Nadine Winter in Ward 6 last September by a few dozen votes, has mounted a similar write-in campaign.

Last Saturday, officials of the D.C. Board of Elections and Ethics discovered they had erroneously instructed 600 absentee voters that their ballots must be mailed back and received by the elections board "not later than 8 p.m., District of Columbia time, on election day, Nov. 7, 1978."

What they meant to tell absentee voters was that ballots must be "postmarked" not later than Nov. 7. During the weekend and yesterday, elections board workers sent out Mailgrams and telegrams to explain the error to absentee voters whose ballots still had not come in. Deputy elections administrator Delores Woods said, however, that more than 400 of the 600 ballots already had been returned by midday yesterday, and more are expected today.

"I don't think it's a very serious problem," she said. If anything, the erroneous instructions would tend to make voters mail their ballots ahead of time, rather than late, she said.

Voters seeking information about election procedures in the District may call the elections board at 347-9725 or the League of Women Voters at 785-2616.

Maryland information is available at the Prince George's County election board, 952-8962 and the Montgomery County board, 279-1507. In Virginia, voters may call election boards in Arlington, 558-2345; Alexandria, 750-6236, and Fairfax County, 385-8100.

The U.S. attorney's offices in Maryland, the District of Columbia and the eastern district of Virginia will be open to take inquiries or complaints concerning possible election irregularities. The number to call in Maryland (Baltimore) is (301) 539-2940. In Washington, it is (202) 755-8719, and in Virginia (Alexandria), the number is 703) 557-9100.

All package liquor stores in Virginia and Maryland will be closed during polling hours. But the stores will be open in the District of Columbia.