With a single tweet, Katy Perry entered the [article id="1635715"]summer-jam sweepstakes[/article], unveiling her [article id="1638572"]brand-new single, "California Gurls,"[/article] to the masses. And, oh, don't think she didn't know it.

"SUMMER STARTS NOW!," Perry shouted ... er ... wrote on her Twitter page. "WHO'S READY TO HEAR MY SINGLE 'CALIFORNIA GURLS' ?"

She then posted a link to her website, which now bears the slogan "Summer Starts Now!" and features a promotional image of a blue-haired Perry reclining on the beach in a bejeweled bikini. Although you can hear "California Gurls" on the site, within minutes of Perry announcing the track, it was practically everywhere on the Net, including Perez Hilton's site and Ryan Seacrest's blog.

Perry wasn't exaggerating when she said the summer starts now, either. "Gurls" is a big, bright, decidedly beach-friendly pop tune, full of sunshiney synthesizers, starry, electronic whooshes and loose, funky, wah-wah guitar flourishes. As if all that weren't enough to guarantee it instant summer-jam success, well, then wait until you hear the positively massive chorus, on which Perry sings about Daisy Dukes-wearing California gurls with "sun-kissed skin so hot [it'll] melt your popsicle." Oh, and Snoop Dogg also shows up midway through to contribute a verse dedicated to the "toned, tanned, fit and ready" Cali girls he loves.

In short: Welcome to your favorite sun-tanning song of 2010.

Co-written by Perry and hitmakers Dr. Luke, Max Martin and Benny Blanco, "Gurls" will hit radio May 25. The tune's debut comes just one day after snippets of it -- and two other songs, "E.T." and "In Between" -- leaked online. There's still no word on what Perry is planning to call the follow-up to her breakthrough One of the Boys album or when it will hit stores.

What do you think of "California Gurls"? Let us know in the comments!