When warm weather comes to the country and stays, leaves and insects burst out, as if they had been spring-loaded. One day there are none, the next they are everywhere. The green curtain falls, bug sounds fill the noon and the night.

In the city, what bursts out are people. They live or work here year-round, of course, so from November to April they were coming and going. But they bundled up in down and scarves, or crouched under umbrellas; they walked with shrugged-up shoulders and quick stiff steps. Outside was like an airport, an unpleasant stage in a journey. When high spring comes, we swarm out and stay, milking every outdoor minute.

Every time of day and every day of the week brings its own cast of hundreds. Drunken girls in high heels and short skirts stagger over sidewalk grates and Belgian blocks. Evangelists for Christianity and Greenpeace hand out leaflets urging you to save your soul and your planet. Buskers make hay while the sun shines. They have to make money all year, but now that it is warm they juggle torches, play music, or demonstrate vegetable slicers with enthusiasm.

Union Square becomes an amphitheater in which the spectators are also part of the attraction. They too are gladiators, to whom we give thumbs up or thumbs down. Look at the art. God, it’s awful. The suckling black women and wise old rabbis vanished long ago, and I think the workers having lunch on the girder 69 stories up have gone too. Now the art of the moment is Japanese line drawings with blobs of color: LeRoy Neiman with kimonos (or, soft-core-ishly, kimonos slipping off). Also popular: a zillion pictures of the Flatiron Building. I love the Flatiron Building, but a zillion of anything is too many. At the southern lip of the square sit the chess players — black Bobby Fischers and Garry Kasparovs. This is real art, or at least skill: no idle pastime, but battle. They move their pieces and hit their clocks with decision. A row of them looks like robots assembling a Saturn, or the hammers of a grand piano.

Skateboards, dude! (Does anyone say dude without air quotes?) Every single skateboarder is a guy; no Title IX here. To my inexpert eye they all seem pretty bad, regularly wiping out and landing on their coccyges. Shouldn’t they be blond and in California? But they get up and go once more unto the breach, once more, rolling down steps and the metal piping of handrails. Younger children are taken by their nannies or parents to swings. They sit buckled in, plump as melons with legs. Their silence suggests contentment; sad New York babies know how to make a racket (practicing for community and co-op boards).

Dog owners can let their pets exercise without suffering hard-weather stress themselves, though they have to watch Fido lest the season make him combative. Just last week I saw a true dog fight: a big, ordinary-looking creature (no pit bull or rottweiler) really giving it to some smaller beast. It was so unexpected that passers-by stopped and gaped. A human broke it up, and hauled the aggressor away by his collar, then laid him down and read him the riot act. No dog whispering here, but a reassertion of dominance.

The farmers’ market no longer feeds a little life with dried tubers. The fishmongers say the blues are running; asparagus, rhubarb, and ramps are ready; garden suppliers have tomato and pepper plants in plastic trays, green and gangly as fourth-graders. Some brazen souls still offer apples that wintered in freezers. Let the dead bury the dead.

Around and throughout the square is café society. There are half a dozen restaurants on Union Square West, from frozen-yogurt shops to kid bars to old reliables. Their outdoor tables run together like a gauntlet; students, white-collars, shoppers, tourists, Brooklynites, and a few bums pass in review before them. Eaters and drinkers are reviewed in their turn: cool, aspiring, plain hungry and thirsty, just living in the neighborhood. Waitresses take orders and wait for the degree, the proposal, or the big audition. In the park are the do-it-yourself diners. They pull up a spindly metal chair or settle onto a long wooden bench with a wrap or a takeout salad, and text, ignore squirrels, or contemplate Mr. Lincoln.

So devoted are we to the great outdoors that when the we’re-not-done-yet cold fronts come through we defy them. Commuters head home in spring-weight jackets and flip-flops, the maîtresse d’ sticks shivering to her post, the partiers party on. Only rain can call time. Sometimes there is the interruption of an event — a demonstration, a corporate promotion, Buddha’s birthday. Late at night, the pace slows a bit. Chains are strung across the entrances to the park — not as barriers, since they are easily stepped over, more as discouragements. I don’t know what the scene is like at dawn, I am never up that early.

Thirty years ago none of it was here. What was here instead was bald dirt and lowlifes hawking smokes and a gangsta disco on one corner that they made rap songs about in the islands. The only festivity I remember was May Day, when little old Communists and Trotskyites came out and abused each others’ newspapers. We elected a mayor with a brain and a spine, and things changed. But things have changed again. Young evangelists, without brains perhaps but with spines of a sort, want to blow it all to caliphate come, and tried most recently in Times Square. And who can blame them? Look at the women, showing themselves to men not their cousin/husbands; at the Christians, Jews, and none-of-the-aboves reveling in their infidelity; whores, Zionists, homos, usurers, abominations of all sorts: Death to them all, and virgins for the exterminator.

So, life is a front line. Being free is not cheap. To all bombers: FU2.