As a confirmed over-packer, I firmly believe that I exist to keep bellmen in business! Having said that, I traveled for two weeks without access to washer & dryer, in a 20" rollaboard and a small shoulder duffle. I'm a shopper, so I packed the rollaboard into a larger (empty) suitcase and checked it. That empty bag was my souvenir bag. It was cheaper to pay the money to ship back an extra bag than it was to mail items back to the States. For the plane, I had the shoulder duffle and a small tote/purse. Those contained a change of clothes, my toiletries and my electronics.
I bought Rick's packing cubes, and all my clothes fit into the large one and a smaller one. A pair of black pants, a pair of black jeans, a pair of blue jeans and maybe a pair of long knit yoga pants for sleeping and to hang out around the flat in should be plenty. Choose the lightest knits you can find - use 3/4 sleeve shirts or long-sleeve shirts under a light sweater - under your coat. Don't try to bring bulky clothes. You can always buy something heavier there if you're freezing!
There are cute TINY umbrellas, and I brought one of those. I would recommend a waterproof jacket with a hood. Bring a thin scarf - like a pashmina-type. You can use it as a muffler, a shawl over another jacket, a light wrap, even as a headscarf. It will roll up into a sandwich-size baggie. Also bring a giant thin pareo-like scarf. Again - it goes in a sandwich baggie. It's your blanket on the plane, your throw in your room, even an extra light blanket on your bed.
I found you can easily pick up more shampoo, etc. But things like Tylenol, Immodium, etc, were harder to come by. Bring your own little baggie of OTC meds. One pair of sturdy walking shoes, one pair of walking shoes that can also go out to dinner and a pair of flip-flops for the shower and for use as bedroom slippers is enough. Don't take a lot of jewelry! I'd leave the "good stuff" at home and take only costume stuff you don't mind losing - and not much of that. Download your books to your iPhone/iPad with the Kindle app. Upload any documents that you might need to a Dropbox account that you can access from your i-devices. Your photos can also be set up to upload to Dropbox when you sync your device.
Bottom line, pack it all and then take half of it out. I did that over and over and still didn't use half of what I took. Good luck!!