When planning your European trip, check your arrival and departure dates and see if they cater for peak, off-peak and shoulder travel periods.
Peak periods are the times when the majority of travelers fly in and out of countries and these periods usually coincide with school holidays, Christmas, Easter and New Year. The country you fly in will also have peak taxes unique to that country, so expect airplanes and accommodation to be heavily booked and tickets to be more expensive. This peak period generally covers the end of December to January (due to the Christmas season) and the end of June to the end of August (summer vacation). Travel during the Christmas holidays can be difficult as airfares float and ski resorts start overcharging. Public transport is also reduced in most areas, as only a few trains will leave on Christmas day. The "shoulder period" is in spring and autumn, and the low or "off-peak" periods are normal in the remaining months and in the winter.
If you only have limited time to see Europe, it's your best chance to fly in and out during a shoulder period. Prices are almost at their lowest and travel conditions are good because you can avoid the crowds and the overpricing. If you have a lot of time to save in Europe, try flying in low season when fares are cheapest so you have more money to spread over your stay. It's always a good idea to start checking airfares 3-4 months before you travel. Airlines start discounting to reward early bookers and there is much time to wait if you think they are too high. The cheapest fares can be displayed online or at your ticket office at any time. And while you are about it, make sure you have already booked your accommodation 6 weeks to 2 months before you travel. It is a good idea to book a hotel for your arrival and departure dates. The rest can be booked afterwards. Also, be sure to check for travel hazards and updates. Your government and insurance company can pull the line if you visit a particular area they have warned you about. Be aware of the dangers and uprisings of the country you visit and make last-minute updates to check the conditions just before you travel.
For most experienced travelers, the best time is to see Europe from April to June and September to October when the weather is still hot, the holiday masses have left, and accommodation and transportation are regularly priced.
By contrast, the only worst time to visit most parts of Europe (especially the western and southern countries) is August. This is where many Europeans leave and take their vacation in nearby countries. The cities can be desolate and as a result house prices rise and it can be very difficult to find a bed. Buses and trains are often packed and it can be a struggle to get space while crossing countries. Even most tourist shops and places can be closed because the owners have also taken vacation! There is no doubt that July and August are the busiest tourist months in Europe (mainly because of Americans on vacation) and it will require a lot of patience and money. Avoid these months as much as possible. If you really have to travel in high season, the best course of action is to stay away from the big cities and choose the off-track towns and villages and indulge in the local culture.