HOLLYWOOD, Calif. — Things are heating up in Southern California, and not just with the outside temperatures.

According to a source, Ashlee Simpson and Pete Wentz are planning to tie the knot this weekend at her parents' house in Encino, Calif.

Simpson, 23, and Wentz, 28, announced their engagement last month.

Earlier this week, a source told Us Weekly that invited guests were asked to keep the wedding festivities on the down low.

"Proper invites have not been sent out, but instead guests have been given a save the date notice," the source told Us, adding that shuttles will transport attendees to the actual wedding location.

Simpson and Wentz, who is the bassist for Fall Out Boy, have been dating since 2006.

Guests attending the couple's big day would be wise to dress comfortably. Temperatures are expected to be in the 90s along the Southern California coast this weekend.