Sunlight,in the end, is merciless.

What was so prayed for in the depths of January, what was so welcome in the glorious days of May, is now the blast furnace of despair. It's 117 in Vegas. In the Midwest, farmers give their livestock cold showers.

In the nation's capital -- a swamp stuck between two rivers -- you walk outside in the morning and the heat smothers you. By noon, the sun melts Popsicles, patience, small children, and the will to live.

There is only one way to survive such hours, and that is to find nature's only mercy of the season -- shade, the lovely shade, the only caress that summer provides.

"Shade is a big-time thing these days," says Michael Jones, a federal government worker, mopping sweat from his brow in Lafayette Park yesterday afternoon. He watches a game of blitz chess at one of the concrete tables set up around the park's walkways, standing about three feet out of the sunlight. "There are days, over in Dupont, where we'll actually pay one of the homeless guys to move from a chess table in the shade."

Why are there odes to the sea, to the stars, to a Grecian urn, and so few to shade? Is it because, like romance, it never lasts? Is it because, like childhood, it is sweeter in memory than reality?

No matter. Watch the multitudes walking to work -- they'll cross the street to be in it, take the sidewalk closest to buildings to hide from the sun. In parks, strangers sit beside one another on benches beneath trees, leaving the wide-open spaces in the sun empty.

Here is Stacy Twersky, reading "The Lovely Bones" on a shady bench in McPherson Square. It is 2 p.m., and, we would estimate, about 732 degrees.

"I don't know what the difference in heat is, but you have to stay in the shade," she says. "Out there, " she gestures to the unshaded areas, "it's just impossible."

You look out there in the glaring sunlight, the orange and yellow marigolds stretching toward the sun. You wonder if marigolds have any sense at all.

Twersky heads back to work, but, since we are too heat-addled to move, let us consider that shade, descendant of Middle English's sceadu, is the land between light and dark. It is the world of in-between in which meaning is determined by the degree of diminished light. There is shade, the good girl of daylight and cool breezes. Then there is her naughty sister, shadow, that which makes dark things possible, some of them alluring in spite of their danger. Or maybe because of.

Without such realms, where would we be? How would we survive the heat of the day, how would our language, our stories, explain the complexities of life?

Example in the negative: November. The sky overhead is the same color as the sidewalk underfoot. Everyone's skin appears to be the hue of an old office building. Shade means nothing in such a season.

Everyone who loves November, raise your hand. Thank you, both of you.

Example in the positive: the magnificent closing scene in "The Godfather, Part II." The once-principled and idealistic Michael Corleone (Al Pacino) sits outside the family mansion in Nevada. It is late afternoon. He has just had Fredo, his dimwitted brother, killed out there on the lake. The camera pulls in slowly, slowly, to a tight close-up. Michael's face is half in the light, half in shade. Good and evil, contained within the same man.

Everyone who loves "The Godfather," raise your hand. Thank you, thank you, everyone.

So maybe we don't just like shadow and shade. Maybe we need them. Maybe they help explain our confused and difficult lives to us. Or, maybe, we've been sitting on this park bench for too long.

So back into the sunlight, the impossible heat. A bus blows by, hot air and grit from the street. Sweat drips. It feels like Calcutta. You let your mind drift, your eyes squint. There, in your fevered imagination, is the day's most delicious bit of shade, twilight, what they used to call, way down south, the gloaming of the evening.

In this daydream, you turn off the street and into a quiet esplanade, a well-tended place with somnolent bars and sultry restaurants. The first star is alight, the sun has faded, and you walk into a courtyard where your lover waits in the deepening shade, a smile on the lips, a breeze coming through the trees, the drink on the table, a soft summer kiss, the falling shadows giving way to the coming night and you are, at last, in the sweet, sweet shade of the day.

From left, Lynette, Doris and Jordan Williams of Rockford, Iowa, enjoy a picnic under a tree on the Mall.James Leslie, front, and co-worker Jason McGraner find shady refuge in Richmond.