.. a varied array of colthing ;-) September in Halifax can be somewhat unpredictable, anywhere form the high 70's to the low 50's. Although the norm is right around 70 and Sunny. This is the running joke here anyways, cause everyone takes their vacations in July and August, then September turns out to be the nicest month of them all ;-))
A decent raincoat would be your most valuable piece of clothing, lots of great things to see in Halifax regardless if it's raining or not.
If ya have any questions about Halifax, just ask away!!!