IN Yakima, Wash., they will circle the county jail, praying for freedom and hope. In Washington, D.C., a rally in Lafayette Park near the White House will urge prayers for the president. Elsewhere, in arching cathedrals and humble community churches, the Oklahoma City tragedy will bring heads to bow.
Set up in 1952 by President Truman in a period widely defined as mainstream ''Protestant-Catholic-Jew,'' the observance now has a decidedly Christian evangelical feel.
This year a concert, ''Seek His Face,'' will be broadcast from Moody Memorial Church in Chicago to 100 TV stations -- reaching millions.
National Day of Prayer Task Force officials in Colorado Springs, Colo., speak in evangelical terms of a spiritual crisis, ''something deeply wrong'' with America.
Spokesman Ken Waggoner argues, ''There is a growing grass-roots sense, underscored by Oklahoma, that we have thrown billions of dollars at problems that are primarily spiritual and moral.''
''Oklahoma calls people to prayer,'' says Cathy Colley, an organizer in Seattle, ''including people who don't normally pray.''
Many backers hope this prayer day will bring a revival inside American churches. Typical is John Dwyer, a Presbyterian and co-publisher of a monthly Christian newspaper in Dallas-Ft. Worth, Texas.
''The American church has become a reflection of the larger culture,'' he says, ''arrogant and self-centered. Churches today want people to feel good -- rather than calling [us] to repent and glorify God.''
Mr. Dwyer is helping to sponsor ''Awaken, America,'' an event designed to celebrate the Christian heritage of the country.
Still, the prayer observance is controversial even among many evangelical Christians, some of whom strongly disagree with a state-sponsored prayer day, and others who feel that prayer extravaganzas are superficial and ultimately misleading.
''If you are seriously Christian, prayer is something you do every day, and you don't want the state sponsoring it,'' says Duke University in Durham, N.C. professor of theology Stanley Hauerwas. ''That reinforces the kind of patriotic civil religion that is exactly the problem.''
''At its best it is like a Puritan fast day,'' says one scholar of American religion. ''At its worst it is like that bumper sticker, 'Honk if you love Jesus.' ''
Whatever the manifestation, prayer day has taken off. Some 37,000 volunteers are putting together 15,000 local events, according to National Task Force figures, and that number is only the formal events. For the first time, all 50 state governors have petititoned their legislatures for a day of prayer.
''The press has been slow to see a tremendous renewal of spirituality ... a rebellion of the human spirit against the mowing down forces of secularization,'' says David Wells, a professor at Gordon-Conwell Seminary in South Hamilton, Mass., of the surge in interest.
Yet Dr. Wells, author of a much-discussed book in the evangelical world, ''No Place for Truth,'' is skeptical of efforts to promote the observance. ''There is no way in these extravaganzas you can engage Christian truth as it ought to be engaged,'' he says. ''Instead you get the event as therapy, without regard for whether it is true.''
''On the heels of Oklahoma, we have to try to understand why we have paranoid people,'' he adds.
''Simply singing patriotic songs that link God and country again is not going to reach the heart of the problem. Our society is fragmenting in fundamental ways, exposing large pockets of alienated, frightened people. Some are intellectuals, some dress up in uniforms and join militias.'' Yet many religious thinkers ambivalent about prayer day support it as long as the day is inclusive of all faiths.
''As a Protestant sectarian, I get a little nervous about a national day of prayer,'' says Chicago Seminary professor Susan Thistlethwaite, who specializes in religious extremist violence against women. ''But in the culture today, maybe it has merit if it shows respect for differences.''
The Continental Congress sponsored the first national prayer day in 1775. But special days of prayer date to the early Puritans, according to Leigh Schmidt, a scholar of religious holidays at Drew University in Madison, N.J.
Local town officials would set aside a day for prayer and fasting, or thanksgiving, in response to a good harvest or a tragedy like an earthquake or fire. Unlike Christmas or Easter, Dr. Schmidt adds, ''prayer day has not yet been commercialized by the trade industries.''
In 1988, President Reagan permanently located prayer day on the first Thursday of May.
''The real significance,'' says one Boston lay minister, ''will be whether people actually pray.''