We are booked on a My Way Alps Tour in September and I am wondering about what to pack. We tend to pack light and dress in layers but even though the lodging locations look like weather should be pretty mild (daytime highs 50-60s F), we will certainly hit temps that are much lower as we venture on our own to higher altitudes. I'm wondering about people on this forum who might have done this tour in September. Did you need big bulky sweaters and parkas? (I might add we live in the California desert where temps are routinely in the 100s.)
Light base layers plus the kind of down jacket that you can squish into a ball should be adequate for mountains. In late October in Switzerland, I was mostly in short sleeves (a record warm year, but maybe less unusual these days).
Do a search on the for for "packing Switzerland" and you'll get lots of great suggestions.
Absolutely no to bulky items if you want to pack light.
Packable down jackets and vests are great and take little room in your bag. Also, a packable waterproof jacket/coat will also cut the wind, wear it alone or over the down jacket. Toss in a pair of gloves or gloves liners and a cap and your ready for anything.
If chilly mornings and evenings are a concern, pack thin but warm base layers. Some options are wool, silk or synthetic like Uniqlo's Heattech line.
I always take a packable puffer when we will be in the mountains. Layer it over a t-shirt of it is mild, or over a lightweight fleece for extra warmth. I often start the day in a wool t-shirt, fleece, and jacket, then peel off as the day progresses.
I wear this lightweight fleece almost year round https://www.llbean.com/llb/shop/129259?page=womens-airlight-full-zip-jacket-womens-petite&feat=airlight%20jacket-SR0&csp=a&attrValue_0=37564&searchTerm=airlight%20jacket&pos=1. Super lightweight, not bulky, and adaptable.
LLBean has many packable jackets although my favorite has been discontinued. Lands End is another good source.
I did this tour last year in Sept. I had planned on taking my puffer jacket and at the last minute I took it out. It was warm and even warmer while walking. Long sleeved tees and a couple of lightweight sweater/sweatshirts were plenty for cooler days. Usually I was in my tee and skort or lightweight pants.