Europe in May

Layers. I take a fleece with me when we typically go in May. That said the last time we were in Northern Germany it was in the 70s and my hubby ended up buying some short sleeves and shorts.

Keep in mind May has a TON of holidays in Germany so keep an eye on that, as things will be closed. Shops are also closed on Sundays.

Agree with layers. Also - if anyone if you are prone to seasonal allergies at all be sure to take some allergy medication from home!

You may also need something for rain and wind protection. I use a lightweight, hooded waterproof jacket. On the coolest days, I use my fleece underneath the jacket. Whether water-resistant is adequate probably depends on your risk tolerance. The recent occasions on which I've really needed something waterproof were all in May (as opposed to June-September), but there's a great deal of luck involved where precipitation is concerned.

May is my favorite month to be in Germany. I have experienced anything from short sleeve and shorts/capris weather to needing a jacket and long sleeves. Most of the time I have needed to have a jacket with me, but to take it off and put it back on at various times of day depending on if the sun was out or not. Make sure to check the forecast shortly before you go. It will be nice and green, and the sun will set fairly late. May is also spargel (asparagus) season in some parts of Germany. You might find this near the Rhine Valley. Look for various white asparagus dishes. They are delicious!

We are Flexabile. Would anybody suggest going in June? Would it be better for where we're going? I doubt Italy would be much different with its climate.

Can you start the trip in Italy, then head north?

You can take a look at actual day-by-day weather over the last 15 or so years on wunderground.com. I've linked to Berlin's stats for May 2017. What can you say about a month that had three days with highs of 50F or 51F, then four days in the 80s (one at 89F)? I see that May 2016 and May 2015 were more moderate at both ends of the scale.

I like Germany in May. My experiences in May there weather wise are similar to that described by Karen. In the Brandenburg area the Spargelsaison starts by mid-May lasting to mid-June. Normally you can expect the weather to be cooler in North Germany than in the Middle Rhine area. In some ways June is better than May, the days being longer, the temperature easier to predict. Between the two I would choose June.

You can be very lucky with weather in Europe in May and when the sun is shining people normally are acting nice too :)
layers are always a good choice!
Bern and Interlaken might be colder then Rome for example!