It’s a matter of preference and comfort. While it may be beautifully sunny or even uncomfortably hot for your entire trip, you’re pretty likely to run into at least some rain and cool weather in the course of several weeks. Europe is generally cooler and wetter than the US in summer. It can get downright cold if you happen to hit a rainy couple of days while you’re in the Alps. You’ll be okay with your hoodie and poncho — if you layer a t-shirt, and something with long sleeves with your hoodie. While the poncho is good to cover both you and your gear in a downpour while you’re traveling I prefer a lightweight, water repellent jacket for a cool, drizzly day of sightseeing — it’s a lot more comfortable than those flimsy ponchos.

If you think the jacket will take up some space than it’s worth, then leave it home. You can always buy a jacket if you’re unlucky enough to hit a long spell of really lousy weather.

great advice. thank you.

Except for the Mediterranean regions of Southern Europe…your chances of a rainy day in July and August are very very slim. You may encounter one day of quick thunder showers at most.

i remember a big downpour one day in Paris in August one year
that was the only day of rain in London and Paris over 10 days
i bring a small umbrella and a light nylon water resistant jacket