Even though Europe’s climate varies vastly through its huge geographic span, the peak season for international tours to Europe is June to August. Summer is a best time to go to Europe given its long hours of sunshine which means you can sightsee for 16 hours or more, but on the flip side, you have to cope with huge crowds, high temperatures and packed hotels.
If you really have no option but to travel during the peak summer season, then travel to the north of Europe to countries like Sweden, Norway, Finland, Denmark, Netherlands, northern Germany, Ireland and the UK. You could also visit the new entrants to Schengen namely Lithuania, Latvia, and Estonia. You will have much better climate there.
Jam packed with tourists in summer, the cost of hotels, tourist services, attractions, etc. sky rocket. All tourist destinations throughout Europe will be more expensive during the peak season.
This makes spring and autumn ideal times to visit, since the crowds would have dispersed and rooms are priced more reasonable and airfares are much cheaper, and the weather is milder.
I would go further and suggest that the best time for Indians is to travel to Europe would be during April and May when the schools are closed here in India and it is the time of the Great Indian Summer, else plan for a trip in mid-September or October which are the shoulder seasons for travel.