The weather in India can vary greatly. For the most part it is hotter in the south, but during the summer months it can be much hotter in the north. There are five seasons in India: winter, December to the end of February; spring, end of February to middle of April; summer, middle of April to middle of July; monsoon, middle of July to middle of September; and fall, middle of September to end of November. For most places, except for the Himalayas, it is best to visit India from October to March. Unless you plan to go to the Himalayas or Nepal, from late April to the beginning of September is a bad time to come to India. From late April to June it is extremely hot. From July to early September, it is rainy and also hot, but not as hot as in June. The winter can be extremely cold in the north and pleasant in the south. During the spring, the weather in the north is very nice. By the end of April, India is very hot everywhere but in the Himalayas. The weather in June is extremely hot, sometimes going above 45°C (113°F). It is not really possible to travel too much at this time. May and June is a good time to visit the Himalayas. The monsoon season (July/Aug/beginning of Sept) is not an ideal time to travel in India, as it rains a lot. India has typical tropical rain, very hard for short periods of times. Sometimes, however, it can rain steadily for days. In Delhi, during the monsoon it does not rain that much, while in Mumbai it rains a lot. Other times of the year it may not rain for eight months straight, except an occasional shower. In September the rains stop in the north and it can be very hot. October and November are ideal weather there. It is still hot, but pleasant, and the rains have stopped, except in some areas in the south. In Delhi, Agra, and Rajasthan, winter (December, January, February) is cold at night, but it can be good during the day. If you are going to be traveling in the north during this time you should bring warm clothing. It does not get as cold as Europe or parts of the USA, but there is virtually no central heating systems in India, so you cannot escape from the cold. If you are active and want to travel around and see the sites, the winter is a good time to visit Rajasthan, Delhi and Varanasi. Summer (April to early July) in Delhi and Rajasthan is extremely hot. The best season in Delhi is spring and fall. There is no rain and the weather is perfect. October, November, and March are the best months. The temperatures in Mumbai, Puri, and Calcutta are nice all year around, but they have a lot of rain during the monsoon (July to the middle of September). In Puri you can swim in the ocean all year around. The Himalayas are extremely cold in the winter, so it is not advised to go there then. The summer months, May and June, are great times to go. Even though it rains in July and August, it is still a good time to go to the Himalayas. The weather is good in September in the Himalayas, but by the middle of October it starts getting cold. Even in the summer, the nights can be cool, and you may need warm clothes all year around, depending on how high up you go. It is good to visit Nepal in March, October and November; the western Himalayas from April to June; and the Indian peninsula and Sri Lanka from November to March.
South Indian Weather
The best time to go to South India is December to mid-February. It is warm and sunny, there is little or no rain, and the temperature rarely goes above 30°C (86°F) or below 13°C. This is the best time to travel, but the hotels may be full and the prices will be higher than normal. Especially from Christmas to New Years, it is very crowded. From the end of February to May, the weather gets hotter and hotter. From April 15 till the end of June is a bad time to travel as it is oppressively hot. The summer monsoon (rainy) season is from June to the end of August. It is still hot, but the rain brings some relief. All day torrential rain is uncommon. It does not rain much in Tamil Nadu in June and July. The weather is fine in Mysore and Bangalore, but there is a lot of rain in Mumbai and Goa. In Tamil Nadu and Andhra Pradesh, they have a southeast monsoon season in October and November. The rainiest months of the year in Chennai and Madurai are October and November.
By far the most popular beaches are in Goa. There is a wide assortment of beaches in Goa for people of all budgets and ways of life. Kovalam is a popular beach in south Kerala. It has a good beach, nice waves, and good accommodations. Varkala in Kerala is becoming increasingly more popular with budget travelers.
Gokarna is a popular place with budget travelers. The beaches near Gokarna are beautiful, but only offer the most basic accommodations. Puri is a nice beach in Orissa. The water is nice for swimming but it is not such a good place for sunbathing. Near Konark, there is a secluded beach, but there are not much facilities. Mamallapuram is a nice place located in Tamil Nadu, but is not so suitable for swimming or sunbathing.
Personally I like beach in Puri. Not only because of its beauty and clean water, but because it is a holy place.