Well, weather is different every year... In gereral terms April in central Europe is famous for a mix of everything. The weather can change VERY quickly from warm sunshine to cool rain or freezing snow (and back). April is ok for travelling, but don't forget to bring a warm, rainproof jacket and/or umbrella.

April is a nice season for the Mediterranean if you want to walk around, see lots of places and sights, go hiking etc., perhaps sometimes even warm enough for the beach, but not yet too hot for activities. I prefer spring to summer for countries like Italy or Spain. But there are no guarantees for sunshine, there may be rainy, chilly days as well. Anyway, it's a lovely season with all those trees and flowers in bloom.

Keep in mind that the two weeks around Easter are considered high season, especially in the South.