Going to the Alps?
Travelling to a place that would see snow capped mountains?
I did that one summer and was totally unprepared for the weather. Spring, Summer, Autumn or Winter, if you go sight seeing and part of the tour includes snow capped mountains, you would certainly need warm enough clothing to help you brave the cold. A fleece sweater or a winter jacket is essential.
You don't have to sacrifice good looks for warmth. Yes, you can keep warm by insulating your clothing with newspaper but that added bulk makes you look fatter. A baggy sweater would keep you warm but you would look ten or twenty pounds heavier in it if you are not careful.
Your best bet would be a sleek ski jacket that would take you beyond the mountain tops. Pick one that you can wear for years. Or even decades if you can maintain your current weight.
What I did back then, was to buy a sweater from a tourist shop, which though was in a color I liked, turned out unflattering because of the fit. Those photos are still with me more than a decade later. My friend came prepared with a sleek jacket and look stunning in those photographs.
It is more than just a vanity thing. If you invest in a great jacket ahead of time, you could always use it for this and future trips. Even if it does not snow where you live, you could wear it over a light t-shirt in heavy air-conditioning or whenever you have to travel to colder climates.
Back to your vacation jacket.
Fashion-wise, pick a jacket that fits you. Something too baggy would make you look fat. A jacket that is too tight would restrict your movement. Something that fits nicely and lets you move your arms freely is ideal.
Next, take note of the color of the jacket. What colors make you look great?
If you look fabulous in that particular shade of blue, get it. If blue makes you look sickly, then avoid blue jackets in shades that do nothing for you.
Red looks great in photos and everyone can wear red, as long as it is the right shade. On a vacation, you would want photos taken to keep as memories of this vacation. Why not wear jackets that would make you look great in these photos?
If you have warm skin tones, that is, you look great in browns, oranges, peaches and gold, a tomato red, a fiery red, orange red or any red with golden undertones would make you look fabulous.
If you have cool skin tones, that is, you look great in black, electric blue and silver, then go for a true red, crimson, watermelon red or any red that has blue undertones.
If you absolutely hate attention, then you probably wouldn't be comfortable in attention grabbing red. Other brights look good on photos too. Pick a color that you look good in and are comfortable wearing.
Choose a jacket that allows you freedom of movement and as well as keeps you warm.
You would want to indulge in whatever activities allowed in that trip, like skiing, or hiking or climbing and the last thing you would want is to tear your jacket or pants when you indulge in these activities. You need a jacket that is durable and allows you to move around freely.
Snow is solid ice, so the jacket and pants you wear should be waterproof on the outside. If you fall in the snow, you don't want your clothes to be soaked as you would catch a chill. You jacket and pants should provide you some protection.
You would sweat when you hike, climb and ski. That is well and good when your body is heated up from the activities. When you cool down after that and stay drenched, you might end up falling sick. It is no fun falling sick while on holiday. Hence, the lining of the jacket should dry quickly, even as it wicks the sweat away.
The top ski jackets, like the ones by north face and mountain hardwear do all that. These are two of the brands I know of when it comes to such jackets.