Katy Perry, John Mayer Split

John Mayer, Katy Perry Credit: http://www.cafepress.com/+big-brother+t-shirts

Talk about hot and cold.

After a couple months of casual dating, John Mayer and Katy Perry have split, multiple sources confirm to Us Weekly.

"She's really upset about it," one insider tells Us.

Echoes another insider: "She is making it seem like it wasn't serious with John, but she is hurt."

Us Weekly first reported the budding romance, with Perry, 27, and Mayer, 34, making an "affectionate" appearance together at Soho House in West Hollywood June 19.

At a Beverly Hills pool party Aug. 4, recently divorced Perry and notorious Lothario Mayer "were all over each other, making out," one observer said.

A pal said earlier this month that the "Teenage Dream" singer was ready to get serious with Mayer.  "She doesn't want to get her heart broken again, but she feels a real connection and wants to see where things go" with Mayer, whose exes include Jennifer Love Hewitt, Jessica Simpson and Jennifer Aniston.

Perry divorced Russell Brand earlier this year, and briefly dated Florence + the Machine rocker Robert Ackroyd in the spring.