Hi Soupy,
Itinerary wise - there is no difference. weatherwise February is late summer, with September the beginning of Spring. You will find it slightly warmer in February with highs in the late 20s, whereas in September, you'll have highs in the mid-20s.
http://www.worldweatheronline.com/ is a great resource for monthly weather averages down to town/city level.
Kindest regards,
Julia
