Where in Europe is it warm enough for a holiday in April?
I have had several holidays in the north of France in March, and found it pleasant. I have also been in the UK in April and early May many times, I love it. So I would say it is certainly warm enough for a holiday. (Some people go to the north of Norway and Finland in winter, for a holiday, so every temperature can be warm enough.) If you want a beach holiday, I guess you will need to go to the Canaries. Maybe you will find the south of Spain, Portugal or Italy, or Greece warm enough, but you will not be able just to lay on the beach that early in the year. If you want to see average temperatures, just enter the name of a town, area or country into your internet search bar and add temperature, there are many sites that have that information.