Also check your manual for a way to adjust how soon it shifts into second. if you messed with that while you had the engine off then you may need to reset it back to factory settings.
I wish I had the Manuel I got the car off of Craigslist and the weird thing is I didn't play with the timing on when it shifts so i have no idea why its messed up
Sounds like it is probably in your tune. You may not have done anything but if the weather conditions changed you may now need to tune the engine to get the proper RPMs to shift.