Time of year effect rent prices?

[Jason Powell]

I recently purchased a multifamily plex with rents way below market rents. I'm raising the rents significantly and expect the tenants to move once their lease is up (November 1 and December 1). How hard is it to find new tenants during this time of year and will it effect the rents I can charge? Ideas on the best way to shift my lease terms so they all end in an ideal time of year (if any)?