Washington ? It could be a jittery summer for anyone who takes every single terrorist warning to heart.

The beach beckons, but there’s always the slender chance of a malevolent scuba diver bobbing in the surf, a shark without fins.

Visitors cover the beach while enjoying the sun and ocean in Rehoboth Beach, Del., on June 15, 2000. It could be a jittery summer for anyone who takes every single terrorist warning to heart this year.

Theme parks rock. But terrorists have thought about making trouble there, at least if they have nothing better to do. An al-Qaida manual found abroad urges “blasting and destroying the places of amusement, immorality and sin,” but adds, “Not a vital target.”

The woods? Promising, but the Army Corps of Engineers has a list of dams in the middle of nowhere that terrorists might find tempting.

Ships, malls, bridges, trains, waterworks, landmarks, monuments and more the possibilities for terrorists, as identified in a series of warnings by the government in recent months, cover just about anywhere Americans live, work, travel and play.

All of it adds up to code yellow the new alert system’s color denoting a significant risk of attack; the color of summer and sunshine, too.

There’s an odd exception in the catalog of recently conveyed threats.

Commercial airliners.

The prospect of another terrorist plot using commercial airliners has not been the subject of a public warning, although it is the reason security has been stepped up since Sept. 11. In December, Richard C. Reid allegedly tried to blow up his flight with explosives in his shoes.

Defense Secretary Donald Rumsfeld says he would not be surprised if terrorists have decided to try something other than airplanes.

“That’s what terrorists do,” he said Monday. “They move across a spectrum looking for ways to achieve their goal. And their goal is to kill innocent men, women and children. And there are lots of ways to do that.”

Varied intelligence resources

Almost every other mode of transportation has had a warning attached to it based on wisps of information authorities are gleaning from al-Qaida captives and from intelligence.

Alerts have come with a bewildering mix of specificity and vagueness. Some are precise as to targets the Orlando, Fla., water supply, the Brooklyn Bridge, the Liberty Bell but vague on method, timing and whether someone in a dank cell might have made it up out of thin air.

Some warnings are, as officials like to say these days, actionable.

There’s the old standby the State Department’s running list of countries Americans should avoid. Currently, 27 countries are on the list. Acting on the warning is simple don’t go there.

Then there are 19 countries or parts of countries where Americans should take extra care.

Plus there’s a worldwide alert citing reports that “extremist individuals are planning additional terrorist actions against U.S. interests. Such actions may be imminent and include suicide operations.”

That alert expires Aug. 17.

So Aug. 18 will dawn safe for Americans abroad?

Probably not. State Department warnings typically come with a time limit and are replaced with fresh ones.

Americans travel anyway

For all the harbingers of trouble, it seems Americans are finding something else actionable their wish to make tracks to the beach, the mountains, big cities and amusement parks.

An AP poll found those to be the most popular destinations, in that order. Three in four respondents said terrorism would not affect their summer plans.

Americans’ wanderlust appears intact even if they don’t wander quite so far.

New Yorkers expect more visitors than last summer. Washington is packed with tourists and hotel occupancy is back to normal, despite the capital’s attraction to terrorist target-pickers on Sept. 11 and thereafter.

Officials think Washington is where terror suspect Jose Padilla wanted to blow up a radioactive dirty bomb if he managed to get his hands on the material.

Wiser but sadder

Last summer, before the attacks, the government was getting clues about impending trouble. A nervous CIA Director George Tenet, for one, confessed he found it hard to sleep. Americans went about their leisure unaware.

This summer, everyone is the wiser, at a terrible cost.

But hunkering down won’t do much good if al-Qaida somehow pulls off certain plots despite America’s relentless attempt to crush it.

Its interests are broad “places of amusement, immorality, and sin” could mean anything from a concert in the park to the corner saloon and not limited to public places.

For example, terrorists are said to have considered renting apartments and blowing them up. Nothing has come of that warning, but it might persuade some queasy couch potatoes to get away after all.