What time of year has the best airfares to Tainan, Taiwan?

My husband and I are saving to purchase airfare tickets to Tainan, Taiwan to visit my sister. It looks like November is the best time of year based on weather. We live in SE Coastal Texas so are aware of hurrricane/tsunami effects and want to avoid that. We are saving for the airfare and want to get a ball park figure of how much we should budget for airfare tickets.