Clothes in July and for Jungfraujoch

I am leaving Edinburgh on Monday and heading for Interlaken I have packed Summer Dresses but I can see the there will be thunderstorms so I will pack a raincoat but will I need to pack Winter items as well especially if I get to see the Jungfraujoch

We stayed in Wengen last July/August and I spent most of the time in t-shirts and shorts/cropped trousers with skirts/dresses for hotel and local.

However when going up the Jungfrau you will definitely need warmer clothes. We (myself, my husband and 3 strapping 6'+ sons) started in trousers & t-shirts/long sleeve tops and added fleece jumpers as we went up, by the time we were at the top we had added hats and in some cases gloves, body warmers/gilets or jackets. Most importantly we had sunglasses and suncream - forget them at your peril! We wore waterproof trekking type trainers/walking shoes which again we were very grateful for when we were playing in the snow - non-slip shoes are essential.

Hello thanks for your response as I am leaving in the morning I do have trainers will these be suitable? What about the altitude did you suffer sickness and I take a blood pressure tablet and unsure weather I can make the trip do you have to travel to the top or stop half way for example I will be staying at the Hotel Du Lac and will ask if they provide jackets as I am travelling alone and do not want to carry heavy clothes I have the dresses and high heels for evening in my hotel and casual dresses and smart walking shoes for day time wear.

Thanks once again