One of the most common questions I get asked by people in the US who have an interest in visiting India is "what would you suggest?". My answer is always another question--what do you want out of your India visit? India and the USA are both very similar in their geographic and cultural diversity, so if one knows in advance what one wants to focus on, it become a lot easier to nail down the places to see.
Regardless of where one goes though, it is important to note that the seasons in India will play a big role in the success of any visit and just like most people probably wouldn't want to visit Alaska in winter, they should probably not go to the Himalayas in winter either. And just like it is better to visit Death Valley, NV in the winter, it is also probably better to visit most of the Indian plains in winter too because they can be almost as hot! What follows is a suggested list of places in India to visit in the different Indian seasons which will help you in planning a visit.
Winter/Fall/Autumn(October - February):
A large part of India, including some of the lower-altitude 'hill stations' like Darjeeling and Shillong in the Northeast and Munnar and Kodaikanal in the South are cool and bracing in winter and fall. There are higher-elevation hill stations like Kullu and Shimla that are snowbound and have winter sports at this time of year. Other places that have pleasant weather at this time are the major metros of Delhi, Mumbai, Chennai, Bangalore and Kolkata along with popular tourist places like Agra, Khajuraho, Jaipur, Kerala and Goa.
Spring/summer (March - September):
You can witness many spring festivals all over India, including Holi, the festival of colors in March. Most of the Himalayan region and its hill stations are the perfect places to visit, including Darjeeling, Mussoorie, Nainital and Shimla. The higher Himalayas in Arunachal Pradesh, Ladakh, Himachal Pradesh, Uttaranchal and Uttar Pradesh, are stunning in the summertime.
The Monsoon season (June - September):
The monsoons, which lash the whole of India with heavy rain, are unique to this part of the world and contrary to expectations, it is possible to both travel during the monsoons as well as enjoy it. This is actually my favorite season because it arrives at the height of a hot, scorching summer and produces the unforgettable scent of fresh, wet earth. Although the first downpours are very heavy, often lasting many days continuously, they do typically taper off after which you can expect rain every day for a couple of hours more or less during the season. The weather can be very unpredictable at this time as also the temperatures. It is always wise to have a light waterproof jacket with a hood handy if not a foldable rain-proof poncho. Mumbai and Kolkata receive the most rain and Delhi, Chennai and Bangalore the least. Incidentally, the rainiest place on earth is Cherrapunji in Meghalaya where it rains every single day of the year!
This list should be used only as a rough guide and is not to suggest that you should not visit the places mentioned during the 'wrong' season. Just as it may be a refreshing change to visit Yellowstone in winter, it may be a pleasant surprise to visit these places "off season".