Travel / Warsaw weather in april? [13]

Hi, I'm from Spain.

Next month, from April 10 to April 15, I'm going to stay at Warsaw.

I'm from the south of Spain, so here it's already hot, around 18-20c during the day. I'm not used to cold, I can't go out when it's too cold. This is the first time I'm going to Poland on this part of the year, so, more or less, how many degrees can I expect on those days?