The tornado that people in Union City talk about the most twisted in from the northwest twenty years ago this week, killing two people and demolishing half the downtown buildings. It blew the cross atop St. Joseph’s Roman Catholic Church into a field six miles away.

Another tornado destroyed the same church in 1896, and another flattened fifteen farmhouses in 1927. Yet another reduced two barns on the edge of Union City to kindling and seemed hell-bent on roaring toward town until it hit the South Canadian River nearby, spun away to the east and died out.

Here in the heart of “Tornado Alley” almost everybody knows that a new tornado will eventually show up on the western horizon. But they also agree on this: There is not much use in being obsessed about it.

“You can’t let it rule your life,” said Leo Radtke, who in 1973 watched from the storm cellar as the house where he was born, as well as his new Chevrolet El Camino, was swept away. “If it hits, it hits, and you just start over again, which is what I did. It’s part of living in this country.”

Where the Winds Collide – ‘This country’ is a swath of the Great Plains stretching diagonally from the Texas Panhandle to southern Iowa where warm, moist winds from the Gulf of Mexico frequently collide with cold, dry winds from the west at this time of year, combining to produce more tornadoes here than in any comparably sized place on earth.

And while most of the attention is understandably focused on communities when they are actually hit, a more typical tableau of life in Tornado Alley is found in places like Union City, a town of about 1,000 people in central Oklahoma, 23 miles west of Oklahoma City. Here and in thousands of communities like it, tornadoes exist not as a present danger but as a grim memory and a future threat.

Early warning? – There have been major advances in the radar equipment that helps meteorologists to detect a tornado while it is forming and to warn of its approach. Because of those advances and improved communications through radio and television, there has been a steady decline in the average number of fatalities caused by tornadoes every year — from 311 people in the 1920’s to 138 in the 1950’s to 56 in the most recent 10-year period, according to the National Severe Storms Forecast Center in Kansas City, Missouri.

But the average warning time is still only 19 minutes, and many tornadoes cannot be detected at all until they hit the ground, meaning that the first warning is an old-fashioned one: a human being sees it and yells. And even when people know it is coming, a tornado remains one of the most destructive hazards of nature, a vortex of winds swirling at up to 300 miles an hour and often churning up everything in its path, making any effort to protect property generally futile. ‘There’s Nothing You Can Do’

“If your home is in the way, you’ve had it — there’s nothing you can do,” said Leo Demmer, 64, who has seen five tornadoes in his lifetime but escaped the path of all of them.

Mr. Demmer, a wheat farmer and cattle rancher, quickly added that he was talking more about property than people, who will almost always be safe if they manage to get underground, perhaps to the kind of storm cellar that sheltered Auntie Em and Uncle Henry when the tornado struck Kansas in the “Wizard of Oz.”

Mr. Demmer should know. As he spoke he was adding two and a half tons of concrete to help anchor his own storm cellar, made of two steel cargo containers sunk into his back yard. “It was frightening, it was beautiful, and here it was coming right at us,” Mr. Demmer said of the 1973 tornado. He snapped a few pictures, then headed for the cellar.

It was 20 years ago, but people who describe the tornado can make it sound as if it hit last week. Several recalled that in the hours and even minutes before the tornado struck, at 4:55 in the afternoon, it seemed like the balmiest of spring days.

A Scrapbook of Memories – “It was just real pretty out,” recalled Odessa Bromlow, the owner of the T&B Country Market, which at the time was a cafe. “I had just been to the beauty shop, and it was time for a shift change — then poof. The wind just started howling.”  As she spoke, she flipped through a scrapbook she had put together full of headlines from the Oklahoma City papers. “Union City Devastated,” said one. “Twister Leaves Trail of Ruin,” read another. A Union City woman died because she could not get the door to her storm cellar open. The other victim was a man named Corp Sanders who had insisted on watching the tornado from a chair on his porch, even as the police officer screamed at him to run for cover.

Most People Stay – But while almost everybody here seems to have vivid memories of the tornado and the daze that settled over the town after it struck, most of those whose property was damaged eventually rebuilt and stayed put. Several people, asked what it was like to live in a place where each spring brought the threat of tornadoes, quickly said it was far preferable to living on either coast of the United States. On the east coast were hurricanes and on the west were earthquakes, they said, both of which can yield a far broader trail of destruction than a tornado.

“As terrible as it was, I’d rather deal with a tornado than an earthquake any day,” said Georgia Rother, the town clerk and treasurer. “With a tornado, at least you can see it coming. You can try to run away from it. With a quake, there’s no place to hide.” Others pointed out that even in Tornado Alley, the chances of getting killed or having a home destroyed by a tornado are very low — about as low as the chance of hitting the jackpot in a state lottery.

Early warning 2 – Many towns, including Union City, have installed emergency warning sirens on their streets — but only after experiencing the terror of a tornado when they did not have such devices.

Earlier this year Catoosa, a suburb of Tulsa, tabled as too expensive a motion to buy used warning sirens from a nearby town that was installing a more modern system. Then, in late April, a tornado struck, killing seven people and causing millions of dollars in damage. This week the neighboring town donated the used sirens to Catoosa.

For those who get their warnings by television, though, some experts fear an altogether different problem: too many warnings. Television stations throughout Kansas and Oklahoma have become ferociously competitive over the years. “Some of them will interrupt programs with a tornado alert at the slightest provocation,” said Frederick P. Ostby, the director of the National Severe Storms Forecast Center. “It’s getting to the point where people feel they can’t see any television program in its entirety during tornado season. People are getting angry about it.”

Mobile homes and fatalism – Here in Union City, when people think about tornadoes at all, it is usually with fatalism. That was especially true in a mobile-home development on the south side of town. At one trailer some old tires and cement blocks were placed on the roof to give the unit a bit more heft if a storm hit. “But I don’t suppose it will make much of a difference,” said Beverly Brookshire, a 48-year-old waitress who lives in the trailer. “If it’s our time, it’s going to hit. I just pray, ‘Lord, don’t let it be our time.’ ” Mobile homes can be unsafe in even the weakest of tornadoes. “There’s kind of a folklore out there that tornadoes actually seek out trailer parks,” said Frederick J. Gadomski, a meteorologist at Pennsylvania State University. “But it’s not that at all. It’s really that because of poor construction, they’re simply more vulnerable.”