The best season to visit Europe varies from region to region. The mild temperature that prevails in the continent is an advantage for people who plan a Europe tour during the off-season. It is better to not visit northern Europe between December and March due to extremely low temperatures and extensive snowfall. Countries of the south see sunny days almost all around the year except for a few winter months. July and August can be uncomfortably hot in southern Europe. Summers is the best time to visit Europe as it is known as the party season by tourists as well as by local people of Europe but this season can be costly for tourists. If you are trying to save something on your trip, skip the peak season and travel between April to June or September to October. For some people, the best time to visit Europe depends on the current season and for some people, it depends on the month of festivals. If so you can plan a trip during Christmas or for concerts held in summers.
During peak season (roughly mid-June through August) i.e. summer is a great time to travel except for the crowds and high temperatures. Sunny weather, long days, and exuberant nightlife turn Europe into a powerful magnet. In much of Europe (especially Italy and France), cities are partially shut down in July and August, when local urbanites take their beach breaks. Some places are best experienced in peak season for example Scandinavia.
From April through mid-June, September, and October brings the advantages of both peak-season and off-season travel. In the shoulder season, you’ll enjoy decent weather, long-enough daylight, fewer crowds, and a local tourist industry still ready to please and entertain but it varies from place to place. When deciding the merits of travelling before or after summer, consider your destination. Both weather and crowds are about the same in spring or fall. Mediterranean Europe is generally green in spring but parched in fall. For hikers, the Alps are better in early fall, because many good hiking trails are still covered with snow through the late spring.
The off-season — generally November through March is great for the budget as you can expect to pay less and airfares are often hundreds of dollars cheaper. Hotels are cheaper due to large vacancies. But in big-city business centres (especially in Berlin, Brussels, and the Scandinavian capitals) are busiest and most expensive in the "off" season. The weather can be miserable — cold, windy, and drizzly and it becomes dark by 5 pm. Make the most out of your limited daylight hours. Some sights close down entirely, and most operate on shorter hours, with darkness often determining the closing time. Winter sightseeing is fine in big cities, which bustle year-round, but it can be frustrating in small tourist towns where it is quiet with many sights and restaurants closing down early.
To conclude, one can visit big cities almost all around the year and still be charmed by the liveliness they offer. Though some things might be closed during the off season but it will not affect the vacation you are planning to enjoy!