Summer hats used to be what women wore to hide their sun-bleached hair. But not the hat wearers at a luncheon at Saks Fifth Avenue yesterday honoring the Meridian House Ball Committee.

"I fell in love with this hat when I first saw it," said Diane Sappenfield, whose face was nearly hidden beneath a shiny black straw. She said she felt guilty about spending $165 on a hat but got her husband to buy it for her birthday.

Evelyn Brandt, who was wearing a veil-trimmed, Stetson-shaped straw hat at the Comtesse Jacqueline de Ribes fashion show and luncheon in Saks' Regency Room, said she wears hats in summer and winter.

While most women wear hats only by day, JoAnn Mason, who had put a pink band on her starched linen hat to match her pink and gray linen outfit, wears them night and day. "They are my favorite accessory. I think they are essential to finish any outfit."

But the real hat collector in the crowd was Melody Gilsey, who said she owns 350 to 400 hats, which she keeps in boxes in a room she turned into a hat closet. She has no problem deciding which hat to wear each day. "First I decide what my mood is for the day, then I pick a hat to go with it." Yesterday's choice was a black straw with a turned-up brim.

Jayne Ikard was wearing a bisected black and white hat with a black and white dotted suit, black and white bag and spectator shoes. "Hats are not for kissing and not for seated luncheons," said Ikard, who kept dodging waiters passing trays during the lunch.

As she left the luncheon, she tossed her hat into the back seat of her car. "This hat's also not for driving a compact car . . . but I love it," she laughed.