Washington: Today - Mostly sunny high in mid to upper 80s, low near 60. Chance of rain is near zero today, 10 per cent tonight. Monday - Mostly sunny highs in mid to upper 80s.

Maryland and Virginia: Today - Sunny, highs in 80s, lows in mid 50s to low 60s. Chance of rain in west today and Monday. Monday - Sunny highs in 80s.

Lower Potomac and Chesapeake Bay: Today - Fair skies with visibility of 5 milies or more through tonight. Winds should be southeasterly at 10 to 14 knots today, southerly at about 10 knots tonight.

Extended Area Outlook: For Tuesday through Thursday - Partly cloudy through period with chance of rain late each day with highs in 80s, lows in 60s through period.

The National Weather Forecast for today - Thundershowers are likely from the western half of the Great Lakes region into the lower Mississippi Valley. Scattered thundershowers are also expected from the Ohio Valley to the south Atlantic Coast. Some showers will also fall over the upper Mississippi Valley and alone the north Pacific Coast. Elsewhere, skies will be clear of partly cloudy. Warmer temperatures are forecast from the central Rockies into the west central plains but it will be a little cooler from North Dakota into Michigan. It will be very warm from the Ohio Valley to the north Atlantic Coast. Seasonable temperatures are expected in other areas.

ALMAC DATA, for Sun., May 21, 1977. Sun rises 5:50 a.m., sets 8:20 p.m.; moon rises 9:36 sets 11:50 p.m. Tides: High 11:32 a.m. and 12:01 a.m. Low 6:01 a.m. and 6:41 p.m. High and low tides at the following locations can be obtained by subtracting the hours indicated from the tides above. Annapolis (3 1/2); Bloody Point Lighthouse (4 1/2); Deale, Md (4 1/2); Colonial Beach (6); Norfolk (1 1/2); Virginia Beach (1); Solomons Island (6 1/2); Point Lookout (7).

The Council of Governments' Air Quality Index for yesterday showed the high reading in the Washington area during the 3 p.m. period was 100 for the pollutant, photochemical oxidants. Index values between 100 and 249 indicate hazardous air quality. When the index exceeds 100 the air becomes hazardous and persons with lung, heart and eye problems should restrict their activity.

The National Weather Service forecasts that the Potomac River stage at Little Falls will remain near 3.2 feet today.

Washington data at 8 p.m. (EDT) yesterday: Highest temperature since 8 a.m. yesterday, 87 degrees at 2:30 p.m. Lowest temperature since midnight, 62 degrees at 6:10 a.m. Excess of temperature since May 1, 73 degrees. Excess of temperature since Jan. 1 173 degrees. Record high temperature for today, 96 degrees in 1941. Record low temperature for today, 39 degrees in 1907. Relative humidity: Maximum, 97 per cent at 4 a.m.; Minimum, 42 per cent at 4 p.m. 24 hour precipitation, none. Deficiency of precipitation since May 1, 1.17 inches. Deficiency of precipitation since Jan. 1, 5.44 inches Highest observed wind since 8 a.m. 14 miles per hour from the S.E. at 4:53 p.m. Peak gust since 3 a.m. 20 miles per hour from the south at 4:15 p.m. Local Temp., Humidity(TABLE) Time(COLUMN)T.(COLUMN)H. 12 mid.(COLUMN)70(COLUMN)79 1 a.m.(COLUMN)68(COLUMN)84 2 a.m.(COLUMN)68(COLUMN)84 3 a.m.(COLUMN)66(COLUMN)90 4 a.m.(COLUMN)64(COLUMN)97 5 a.m.(COLUMN)64(COLUMN)97 6 a.m.(COLUMN)63(COLUMN)97 7 a.m.(COLUMN)64(COLUMN)93 8 a.m.(COLUMN)68(COLUMN)84 9 a.m.(COLUMN)72(COLUMN)73 10 a.m.(COLUMN)75(COLUMN)67 11 a.m.(COLUMN)79(COLUMN)54 12 noon(COLUMN)82(COLUMN)46 1 p.m.(COLUMN)83(COLUMN)44 2 p.m.(COLUMN)85(COLUMN)43 3 p.m.(COLUMN)86(COLUMN)42 4 p.m.(COLUMN)86(COLUMN)42 5 p.m.(COLUMN)86(COLUMN)42(END TABLE) Temperatures ending 8 a.m. (EDT) Yesterday(TABLE) City(COLUMN)H.(COLUMN)L. Albany(COLUMN)83(COLUMN)60 Albuqueraque(COLUMN)71(COLUMN)39 AMarillo(COLUMN)66(COLUMN)50 Anchorage(COLUMN)53(COLUMN)40 Asheville(COLUMN)79(COLUMN)54 Atlanta(COLUMN)87(COLUMN)60 Atlantic City(COLUMN)63(COLUMN)60 Austin(COLUMN)81(COLUMN)63 Baltimore(COLUMN)85(COLUMN)56 Billings(COLUMN)93(COLUMN)67 Bismarck(COLUMN)72(COLUMN)40 Boise(COLUMN)70(COLUMN)48 Boston(COLUMN)80(COLUMN)59 Brownsville(COLUMN)88(COLUMN)78 Buffalo(COLUMN)84(COLUMN)60 Burlington, Vt.(COLUMN)82(COLUMN)56 Casper(COLUMN)60(COLUMN)34 Charleston, S.C.(COLUMN)82(COLUMN)68 Charleston, W.V.(COLUMN)88(COLUMN)57 Charlotte, N.C.(COLUMN)83(COLUMN)64 Cheyenne(COLUMN)52(COLUMN)38 Chicago(COLUMN)95(COLUMN)69 Cincinnati(COLUMN)87(COLUMN)66 Cleveland(COLUMN)85(COLUMN)59 Columbia, S.C.(COLUMN)87(COLUMN)65 Columbus, Ohio(COLUMN)89(COLUMN)65 Dal.-Ft.Worth(COLUMN)86(COLUMN)61 Dayton(COLUMN)90(COLUMN)65 Denver(COLUMN)57(COLUMN)38 Des Monies(COLUMN)72(COLUMN)61 Detroit(COLUMN)91(COLUMN)58 Duluth(COLUMN)63(COLUMN)41 El Paso(COLUMN)76(COLUMN)57 Fairbanks(COLUMN)57(COLUMN)43 Fargo(COLUMN)76(COLUMN)50 Flagstaff(COLUMN)64(COLUMN)29 Great Falls(COLUMN)64(COLUMN)29 Hartford(COLUMN)87(COLUMN)58 Helena(COLUMN)60(COLUMN)36 Honolulu(COLUMN)85(COLUMN)74 Houston(COLUMN)82(COLUMN)74 Indianapolis(COLUMN)90(COLUMN)68 Jackson, Miss.(COLUMN)90(COLUMN)62 Jacksonville(COLUMN)90(COLUMN)61 Juneau(COLUMN)53(COLUMN)41 Kansas City(COLUMN)76(COLUMN)65 Las Vegas(COLUMN)85(COLUMN)56 Little Rock(COLUMN)89(COLUMN)68 Los Angeles(COLUMN)80(COLUMN)58 Louisville(COLUMN)89(COLUMN)65 Memphis(COLUMN)91(COLUMN)68 Miami Beach(COLUMN)78(COLUMN)74 Midland(COLUMN)91(COLUMN)63 Milwaukee(COLUMN)82(COLUMN)58 Mpls.-St. Paul(COLUMN)74(COLUMN)50 Nashville(COLUMN)90(COLUMN)64 New Orleans(COLUMN)86(COLUMN)66 New York(COLUMN)81(COLUMN)64 Norfolk(COLUMN)69(COLUMN)58 North Platte(COLUMN)69(COLUMN)52 OKlahoma City(COLUMN)73(COLUMN)58 Omaha(COLUMN)78(COLUMN)65 Orlando(COLUMN)89(COLUMN)62 Philadelphia(COLUMN)82(COLUMN)61 Phoenix(COLUMN)91(COLUMN)67 Pittsburgh(COLUMN)84(COLUMN)61 Portland, Me.(COLUMN)73(COLUMN)47 Portland, Ore.(COLUMN)67(COLUMN)55 Raleigh(COLUMN)82(COLUMN)56 Rapid City(COLUMN)66(COLUMN)50 Reno(COLUMN)75(COLUMN)39 Richmond(COLUMN)83(COLUMN)53 St. Louis(COLUMN)87(COLUMN)63 St. Prbq.-Tampa(COLUMN)87(COLUMN)64 Salt Lake City(COLUMN)62(COLUMN)41 San Antonio(COLUMN)81(COLUMN)60 San Diego(COLUMN)71(COLUMN)58 San Francisco(COLUMN)60(COLUMN)50 San Juan, P.R.(COLUMN)87(COLUMN)76 St. Ste. Marie(COLUMN)78(COLUMN)55 Seattle(COLUMN)72(COLUMN)52 Shreveport(COLUMN)86(COLUMN)67 Sioux Falls(COLUMN)75(COLUMN)60 Spokane(COLUMN)66(COLUMN)51 Syracuse(COLUMN)80(COLUMN)50 Topeka(COLUMN)76(COLUMN)63 Tucson(COLUMN)83(COLUMN)56 Tulsa(COLUMN)83(COLUMN)62 Washington(COLUMN)86(COLUMN)62 Wichita(COLUMN)68(COLUMN)58(END TABLE) Temperatures Abroad Yesterday(TABLE) City(COLUMN)Weather(COLUMN)Time(COLUMN)T. Aberdeen(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)64 Amsterdam(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)55 Ankara(COLUMN)clear(COLUMN)3 p.m.(COLUMN)72 Athens(COLUMN)cloudy(COLUMN)2 p.m.(COLUMN)86 Auckland(COLUMN)cloudy(COLUMN)midnight(COLUMN)59 Berlin(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)50 Birmingham(COLUMN)clear(COLUMN)1 p.m.(COLUMN)63 Brussels(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)46 Cairo(COLUMN)clear(COLUMN)2 p.m.(COLUMN)90 Casablanca(COLUMN)clear(COLUMN)noon(COLUMN)68 Copenhagen(COLUMN)clear(COLUMN)1 p.m.(COLUMN)63 Dublin(COLUMN)clear(COLUMN)1 p.m.(COLUMN)59 Geneva(COLUMN)clear(COLUMN)1 p.m.(COLUMN)64 Hong Kong(COLUMN)cloudy(COLUMN)8 p.m.(COLUMN)79 LIsbon(COLUMN)clear(COLUMN)noon(COLUMN)70 London(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)63 Madrid(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)61 Malta(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)73 Manila(COLUMN)cloudy(COLUMN)8 p.m.(COLUMN)84 Moscow(COLUMN)cloudy(COLUMN)3 p.m.(COLUMN)61 New Delhi(COLUMN)clear(COLUMN)5 p.m.(COLUMN)106 Nice(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)64 Oslo(COLUMN)clear(COLUMN)1 p.m.(COLUMN)66 Paris(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)55 Peking(COLUMN)cloudy(COLUMN)8 p.m.(COLUMN)66 Rome(COLUMN)clear(COLUMN)1 p.m.(COLUMN)72 Saigon(COLUMN)cloudy(COLUMN)8 p.m.(COLUMN)86 Sofia(COLUMN)clear(COLUMN)2 p.m.(COLUMN)81 Stockholm(COLUMN)clear(COLUMN)1 p.m.(COLUMN)63 Tel Aviv(COLUMN)clear(COLUMN)2 p.m.(COLUMN)90 Tokyo(COLUMN)cloudy(COLUMN)9 p.m.(COLUMN)59 Tunis(COLUMN)clear(COLUMN)1 p.m.(COLUMN)81 Vienna(COLUMN)clear(COLUMN)1 p.m.(COLUMN)73 Warsaw(COLUMN)cloudy(COLUMN)1 p.m.(COLUMN)61(END TABLE) Temperatures (Western Hemisphere)(TABLE) City(COLUMN)Weather(COLUMN)High(COLUMN)Low Acapulso(COLUMN)Cloudy(COLUMN)91(COLUMN)78 Barbados(COLUMN)cloudy(COLUMN)86(COLUMN)78 Bermuda(COLUMN)Cloudy(COLUMN)74(COLUMN)68 Bogota(COLUMN)pt. cldy(COLUMN)66(COLUMN)48 Calgary(COLUMN)pt. cldy(COLUMN)66(COLUMN)43 Culiacan(COLUMN)pt. cldy(COLUMN)95(COLUMN)60 Edmonton(COLUMN)pt. cldy(COLUMN)64(COLUMN)37 Havana(COLUMN)sunny(COLUMN)82(COLUMN)71 Kingston(COLUMN)pt. cldy(COLUMN)84(COLUMN)75 Montego Bay(COLUMN)cloudy(COLUMN)84(COLUMN)71 Mexico City(COLUMN)sunny(COLUMN)82(COLUMN)57 Monterrey(COLUMN)pt. cldy(COLUMN)81(COLUMN)73 Montreal(COLUMN)clear(COLUMN)79(COLUMN)55 Nassau(COLUMN)rain(COLUMN)82(COLUMN)71 Ottawa(COLUMN)clear(COLUMN)79(COLUMN)59 Regina(COLUMN)clear(COLUMN)63(COLUMN)43 St. Kittis(COLUMN)pt. cldy(COLUMN)88(COLUMN)77 St. Thomas(COLUMN)cloudy(COLUMN)86(COLUMN)79 Toronto(COLUMN)clear(COLUMN)81(COLUMN)54 Vancouver(COLUMN)pt. cldy(COLUMN)61(COLUMN)48 Vercruz(COLUMN)pt. cldy(COLUMN)91(COLUMN)77 Winnipeg(COLUMN)cloudy(COLUMN)70(COLUMN)48(END TABLE)