It is time for pesky little flying things to make it unwise to open windows and enjoy warm breezes. So you might as well get your screens ready.

If the screens in your house are more than a few years old, they'll probably need some attention. Dirty screens can be cleaned and torn screens can be repaired. It is only the badly stretched or deteriorated screens that must be replaced.

Start with cleaning. The three things you might have to remove from a screen are dust, grease and corrosion.

The first is easiest. Use a soft brush attachment on a vacuum cleaner and brush both sides of the screen lighty. If you have to use much force, try washing.

Screens used in kitchens and other areas where grease and oil are prevalent may pick up a thin, sticky film that attracts dust. This attracts more oil and eventually, the layers clog the screen.

When washing a screen, the less force applied to the screen surface the less likely it is to stretch and collect unsightly waves.

Spray cleaners such as Formula 409 and Fantastik work best on screens, but they can be wasteful. If you stack the screens several deep and spray through the lot, whatever is wasted on the first will hit the second.

Let the solvents in the cleaner do their work for a few minutes and then use a soft scrub brush to loosen the remaining dirt. Place the screen against something firm for support so you do not stretch it while brushing.

Rinse thoroughly. You may use either a light stream from a hose or dip it in a large tub of clean water. A child's wading pool is excellent.

Washing also serves to remove most corrosion, but in severe cases, a wire brush or light sandpaper may help.

Screen repairs are a bit tougher than cleaning.

A quick temporary repair of a screen can be made with clear plastic tape. Apply the tape from both sides; it will stick to itself where the screen is open and stay for some time. While the repair may not look too good, it may last a few months.

If the problem is a hole made by a sharp object, you may be able to straighten the strands of the screen if they are not broken.

For more permanent repair, some of the skills of the weaver may be necessary.

Metal screens can be patched with a piece of screen similar to the original.

Cut a patch three inches larger than the hole. Remove the cross wires from the edges one inch all around the patch. Bend the remaining wires perpendicular to the patch and insert in the screen, making sure no more than one wire goes into each hole. Bend over the wires that protrude through the screen over and the patch is finished.

On plastic screens, a length of light nylon thread and a sewing needle will do the trick. Just weave the thread in and out of the screen pattern, starting a half inch from the hole and finishing a half inch past the other side.

On both metal and plastic screens, patches can be sewn in place with nylon thread.