Just one (atypical) cautionary tale here:
I was flying from SE Alaska to my home, connecting in Seattle right before Christmas a few years ago--the year that a winter storm came through and ended up shutting down the Seattle and Portland airports. A family with small children boarded the plane in Alaska, with the mom in t-shirt and shorts, and the kids had on dresses with tights. One of the mom's friends saw her on the plane and asked, "where is your coat?" The lady said, 'Oh, we're going to Hawaii, we only need our coats up to when we get to the airport in Alaska, so why lug them around?"
Well...we were the last flight to leave that airport for several days. We took off with the intent to land in Seattle, and got diverted to Spokane, where there was 2 feet of snow on the ground. The routes to Hawaii for that family all go out of Seattle and Portland. The lines of people trying to rebook on all airlines, but especially Alaska Air, were very long...you see, they can't just make up new routes and all of a sudden decide they're going to add a Spokane--> XXX route. I heard many people talking about 3 days wait to get out of there. And they couldn't even drive back over to Seattle, as the main highway that goes over the mountains was closed.
What that family did with no winter clothing and no way to get to Hawaii for a few days, I'm not sure. I was fortunate in that I could buy a ticket on a different airline and continue my journey south out of the snow....
So...while this is an exception, it lends a bit of support to people who suggest you at least bring a jacket, if not your heavy winter coat. Sometimes your plane doesn't land in the town you were heading for.
