Best time to travel to Europe

After having travelled around Europe during every season and almost every month I would say, without a doubt, the best time is between mid April to mid June. (unless of course you specifically want to see snow and be here for the festivities of Christmas).

The weather is super nice during this time. You can also easily get sunny 20-25° days during these months in most cities/countries.

Even though the weather is also nice during July and August, riding on public transport and staying in places without air-conditioning can be horrific. Also, during the height of summer it can get exceedingly crowded at touristy cities/attractions.