Really not the same as UK.
We went last week of October. Beginning of the week we were out in the evening in jumpers (thermals underneath but still just jumpers on top). By the end of the week it was all down layers, wolly hats and gloves. The next week was forecast snow and the tour guides were all putting their snow tyres on.
As other people have mentioned auschwitz is brutally cold. The windchill factor is massive on and around the river, up the Castle or at auschwitz. Its worth thinking about whether your layers are WIND resistant not just cold. I was warmer in a down coat with wind proof waterproof coat on top than DD in just a super warm superdry coat.
That had fabulous wool products out there. In the markets we upgraded DD scarf and socks, ( bought a beautifully wool blanket at remarkably cheap price).
We took a small fold away holdall to pile all the warm stuff in when we weren't wearing it, in restaurants etc.
Take sunglasses the sun can be bright.
We were still often sat out in the evening despite the cold. The square was often lovely outside in the evening.