You do not need to wear different outfits. Cultural or Autumn formal attire are appropriate for both ceremonies. If you'd like to wear two different looks though, you are more than welcome to.
You are welcome to wear Indian cultural clothing or Western attire. If you choose the cultural route, for women you would look for a lehenga, saree, or salwar kameez. And for the men you would look for a kurta or sherwani. **DO NOT WEAR RED**. In Bengali weddings, red is reserved for the bride.
Yes. Based on historical data, there is a 51% chance of measurable rain on our wedding day. In fact, November is the wettest month of the year. This means you are very likely to have a very typical Seattle experience! Fortunately, the events will be indoors.