It's summer in every scene in the film, except when Gary is walking home and is offered a ride by Adam. Then, it's clearly fall.
In the pivotal scene when Gary Catell takes the call from his daughter Sarah (she identifies herself by her preferred nickname, Nova) on his radio call-in program and she then commits suicide by gunshot as he listens, Catell visibly flinches in reaction to what would be the sound of the gunshot half a second before the sound of the gunshot is audibly heard.