+1 on the Tilley hats, all four seasons.

Spring, summer, & fall is an LTM6. Stiff enough to keep the sun & rain off. Packing it is simple for me: hat goes on head. But seriously if you do have to pack it, put it on the bottom of the suitcase & pack everything on top of it. The hat will flatten & recover with no problem. Durability is superb. Tilley has a lifetime warranty on their unbleached hats if they ever wear out, mildew or shrink. One of the stories that they include with the hat is about one that was eaten by an elephant. The owner recovered it after it came out the other end. He wrote them about it, they offered to replace it & he turned them down.

Winter is a TW2. It won't flatten out as well for packing but I wear it anywhere & everywhere. It's a good weight wool hat & if the weather is really cold, it has an ears/back of head flap and forehead warmer.