WHAT a difference a summer makes.

In the three months since “American Idol” winner Kelly Clarkson rocketed from waiting tables to a TV-made diva, her personal style has gone from gum-popping girl next door to bi-costal chic.

Look at these photos.

The one on the left was taken last June, just when Kelly arrived in L.A. from Burleso, Tex.

Her hairstyle is mall-rat messy and her make-up accentuates a hard jaw line and sharp nose.

Now look at how she looked yesterday (photo right) running between “Today” – where she was scheduled to sing but was too pooped to croon – and “Live with Regis and Kelly.”

Under the care of a legion of network TV stylists, her look has gone from gunk to glow.

Her hair has been streaked to the shade of a light honey. And her make-up has softened the outlines of her face.

Sources say Kelly did not have much say in her “Idol” makeover. She was too busy rehearsing and getting ready to perform.

She’d just plop herself in a chair just before showtime every week and let the stylist work their magic, said the sources.

“Today” show had advertised all week that the winner of Wednesday’s “American Idol” finale – which turned out to be Clarkson – would sing on the show outside in the plaza in Rockefeller Center, but fans yesterday had to be happy with just an interview.

“Her voice was shot – apparently, she’s been singing like crazy for the past five weeks,” said “Today” show spokeswoman Allison Gollust.

Live Friday concerts are a summer staple of the “Today” show.

“Kelly was intending to sing but there was no question she had no voice left,” Gollust said. “It was pretty scratchy and rough.”

Clarkson was interviewed indoors by Couric, and was then brought outside, where “Today” had set up a stage for the intended performance.

“We invited fans to come over and then we had [‘Idol’ runner-up] Justin [Guarini] come on with her,” Gollust said.

“We’ll have her back on the show when her album debuts” in November.

After leaving “Today,” Clarkson made an appearance on “Live with Regis & Kelly.”

“Live” co-host Regis Philbin tried to get Clarkson to sing a duet with him, but she turned him down too.

But there’s still a chance Clarkson and Philbin will sing together.

Tom Cantone, entertainment director at Foxwoods Hotel & Casino – where Philbin performs regularly – wants to book Regis and Clarkson for the first Saturday in November.

And Clarkson was praised yesterday by the “Queen of Soul,” Aretha Franklin, who will be performing tomorrow at the U.S. Open in Queens.

“She impressed me as someone whom Broadway and the pop world would be calling,” Franklin said.

“I think she has a lot of potential to be an enduring and established artist, and a real favorite.”