There are two basic possibilities here. Either the writers messed up and this is a continuity error, or the three months account for the time difference.
Assuming it's not the first one, let me try to explain the second option. Firstly, “Spring Break” usually coincides with Easter, and depending on the year, Catholic Easter tends to fall between late March and late April. In 2003, the year The Waking Dead comics started coming out on, and the year the game (presumably) takes place in (judging from the boxy “new” TVs on sale in Macon and the lack of smart-phones), Catholic Easter was on April 20th (according to Wikipedia:
http://en.wikipedia.org/wiki/Easter#Reform_of_the_date). Let's assume that Sandra's Spring Break was in late April, and that it was about to begin when Clementine's mom made those calls, not long before Lee found Clementine. Fast forward 3 months, and it's late July. Give the writers the benefit of the doubt, and add a couple of weeks so that the time still rounds to 3 months, and it's still mid August.
There is, however, the possibility that Fall came early that year from all the junk in the air from all the fires that started all over the world in the initial panic (or fires started by lightning that no fire departments were around to put out). Max Brooks talks about this in WWZ to explain the unusually cold winters survivors had to face. Think it's too far fetched? 1816 was known as the “year without a summer” because of a global drop in temperatures caused in part by ash released from the explosion of a volcano in Indonesia (
http://en.wikipedia.org/wiki/Year_Without_a_Summer). I'm not a botanist, and I don't know how the seasons change in Georgia, but my guess is that a drop in global temperatures could cause leaves to turn red and yellow a month before they're supposed to.
I don't know if the writers thought exactly all of this out, but my point is that the continuity is plausible...
Except for the fact that that the date on the tapes is October 10th, as staticfl pointed out. And the doctor in Crawford says on one of his tapes that “this is day 82 since the outbreak” (
http://www.youtube.com/watch?v=aYENrBC0xuk), which on the 2003 calendar, places the day of Lee's car crash (assuming it was on “outbreak day”) on Sunday, July 27th. No school district that I'm aware of schedules spring break in late July.
So yes, the writers goofed.
Telltale Games could use a
continuity consultant, who's only job is to nitpick with little things like dates and times, and
whether or not Lee still has a gun in his back pocket when Clementine gives him his only one back to shoot a walker (Episode 3, in the station). It's a shame when little things mess up the credibility of such an awesome story. And “yes, but zombies...” isn't an excuse for three months to be five months at the same time.