"Hurry!" calls the hostess, "come eat dinner before it gets hot."

A new problem to add to baked and cracked gardens, wrinkled clothes and wilted personalities. How do you keep cold foods when it's 100 degrees in the shade?

If we can have hot trays, why not cold trays, reasoned one host who kept his main course chilled by resting it on a bed of those flat blue plastic containters which you freeze and which then stay icy for a dog's age.

Another way is to choose foods that won't wilt quite as visibly as, for instance, an aspic which may run right off the table, or delicate mousses which need to be cold to hold their shape, or any chicken liver pate which incorporates butter, since the butter will melt and the pate turn gooey.

It also is wise in this weather to avoid even the minimal last-minute cooking. It may seem but a small matter to bring a pan to the boil and dump in corn-on-the-cob, but it's amazing how much heat even such a simple operation can generate. Following are some make-ahead menus which can be served at room temperature:

Ratatouille can be a main course, with a selection of cheeses and French bread. In a good ratatouille, the eggplant, zucchini and peppers all are cooked separately before being joined in the sauce, to preserve their individual shapes and flavors. Be prepared to spend a lot of time at the stove on the day before you plan to serve it.

Cold roast loin of pork is delicious with a chilled cumberland sauce in which you have first poached sliced fresh peaches. With it offer a salad of garden-grown tomatoes tossed with fresh basil and dressed lightly with a vinaigrette.

Thin slices of cold roast beef tenderloin can be served with a horseradish sauce and a side dish of baby beets vinaigrette. The white sauce and the red beets look pretty too, even if, as often happens, they run together and turn everything pale pink.

Cold leg of lamb is good with a side dish of peach chutney and a salad composed of thin slices of cooked potatoes (don't overcook or they'll turn mushy when you try to slice them), tossed with parsley, chives and a little mint, dressed with a thin mustard mayonaise and served on a bed of watercress.

There is little cooking involved in preparing a platter of stuffed vegetables : tomatoes seeded and filled with an eggpant puree (put the flesh of a cooked and seeded eggplant through a food mill, add a crushed garlic clove, 1 tablespoon olive oil and lemon juice, salt and pepper to taste); deviled eggs; cucumbers peeled, seeded and filled with a mixture of tuna fish, mayonaise, curry powder and capers; celery stuffed with gorgonzola cheese softened with either a little butter or cream or, for a tangier flavor, Port; and figs wrapped around with thin slices of country ham.

When it's too hot for anything else, serve a fruit plate, centered with a melon half filled with bluberries and surrounded with cherries, strawberries and apricots. A dark chewy bread and Montrachet cheese provide a tasty accompaniment.

Remember though, that no food, particularly those with a mayonnaise base, should be left to sit out endlessly in the heat of a Washington summer.