My Harris Tweed Sportscoat is definately winterwieght wool.
Don’t get brass buttons.
You want the material and cut of the jacket to attract attention - not the buttons.
You do on a blazer. They look far better on a blazer than horn or plastic.
Only if you’re on a yacht with the silly little captain’s cap on.
Brass buttons on a blue blazer aren’t just for commodore wannabes. I think it’s a good look. Ben Silver has a lot of blazer-button options, including military branches, colleges and universities, etc., but it can get pricey: Ben Silver Blazer Buttons and Cufflinks - The Ben Silver Collection
Seersucker, which used to be only blue-on-white but now is available in a lot of color combinations, is also a good sportcoat option in hot climates.
Lands End has good-quality men’s clothes at reasonable prices. Here are five pages of sportcoats for your delectation, Paul in Saudi: http://landsend.com/cgi-bin/search.cgi?search=sportcoat&store=le&sort=popularity&tab=men&page=1&returncount=1&refer=/cd/frontdoor/&CM_MERCH=SRCH&sid=8795114439912165090&bc=1
I suppose this might be possible in Virginia, but I assure you that no such distinction appears in northern New York or in any other cold climate. Most sportcoats are winter-weight. Finding good summer-weight ones is harder.
And cashmere sportcoats, which are the best if you can afford them, are definitely not summer-weight.
You may want to try this site
Great source of info on all things sartorial
They’ve got forums and everything.