Eastern Central Europe trip, help with what to pack for May

I was in Poland and Budapest in May 2019. The weather was unpredictable. On some days, it was a little hot, while the rest was cool. Can't really predict the weather, and so I think wearing layers is the best.

In most of the region early may or late May does make a difference. Bring a layer or 3 as the temps can range from 55F when you wake to 75F in the mid afternoon. A rain shell will be useful too. Generally a nice time to be here.

https://weatherspark.com/m/84771/6/Average-Weather-in-June-in-Budapest-Hungary

I know you're asking about May, but I think unpredictable weather is the name of the game. In Warsaw and Krakow in July 2018, I stifled in nearly 90 F, high humidity temperatures. The following July, I shivered my way through a return trip to Warsaw and was even hailed on one day. Bring versatile, breathable layers, a good windbreaker/rain jacket, and shoes that can handle wet cobblestones.

Also, have an amazing time! I love Central Europe, especially Poland!

Caroline