Do you need to know, when is the best time to go to India? Then you should take a look here, what weather you can expect there during the year.
India is a huge country, so the climate of India varies - from tropical monsoon in south to temperate in north. There is arid desert in the west, tundra and glaciers in the north, and humid tropical regions in the southwest. Four main seasons can be distinguished here: winter from December to February, summer from March to May, a monsoon rainy season from June to September, and a post-monsoon period from October to November.
As India has a really huge area, the information below relate mostly only to the area around the capital of this country. To see information about other places, please, choose one of these areas: East, Himalayan North, North-East, Plains, South, West.
Let's look now what weather you can expect in the area around the capital and in many other cities. The warmest month here is May, the average maximum temperature is 40.7 ℃ (105.26 ℉). The average minimum temperature in this month is 26.5 ℃ (79.7 ℉). The coldest month here is January, the average maximum temperature is 21.3 ℃ (70.34 ℉). The average minimum temperature in this month is 8.1 ℃ (46.58 ℉). 
When travelling to some places in India, always consider the altitude of the the place as well. The highest point here is Kanchenjunga (8586 m) and the lowest point is Indian Ocean (0 m). So there are huge differences in altitudes in this country and the weather is very different in them therefore. Keep in mind, that the temperature usually decreases by 1.2 - 1.9 ℃ (2.2 - 3.5 ℉) per 200 m (656 ft), depending on the other conditions. (And we should add, that in the very special condition named thermal inversion even the temperature may be higher in higher altitudes.)
Typical (usual) weather in India in January is this: The average highest temperature in India in January is 21.3 ℃ (70.34 ℉). The average lowest temperature is 8.1 ℃ (46.58 ℉). At the beginning of January you can expect higher temperatures, the average highest temperature is around 22.25 ℃ (72.05 ℉). At the end of January you can expect higher temperatures, the average highest temperature is around 22.6 ℃ (72.68 ℉). The average rainfall is 21 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 10:21 (hours and minutes), in the middle of the month 10:31 and at the end of the month 10:48.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.
Typical (usual) weather in India in February is this: The average highest temperature in India in February is 23.9 ℃ (75.02 ℉). The average lowest temperature is 10.7 ℃ (51.26 ℉). At the beginning of February you can expect lower temperatures, the average highest temperature is around 22.6 ℃ (72.68 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 27.15 ℃ (80.87 ℉). The average rainfall is 21 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 10:48 (hours and minutes), in the middle of the month 11:10 and at the end of the month 11:34.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.
Typical (usual) weather in India in March is this: The average highest temperature in India in March is 30.4 ℃ (86.72 ℉). The average lowest temperature is 15.4 ℃ (59.72 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 27.15 ℃ (80.87 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 33.75 ℃ (92.75 ℉). The average rainfall is 14.2 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:34 (hours and minutes), in the middle of the month 12:00 and at the end of the month 12:26.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in April is this: The average highest temperature in India in April is 37.1 ℃ (98.78 ℉). The average lowest temperature is 21.2 ℃ (70.16 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 33.75 ℃ (92.75 ℉). At the end of April you can expect higher temperatures, the average highest temperature is around 38.9 ℃ (102.02 ℉). The average rainfall is 10.7 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:26 (hours and minutes), in the middle of the month 12:51 and at the end of the month 13:14.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in May is this: The average highest temperature in India in May is 40.7 ℃ (105.26 ℉). The average lowest temperature is 26.5 ℃ (79.7 ℉). At the beginning of May you can expect lower temperatures, the average highest temperature is around 38.9 ℃ (102.02 ℉). At the end of May you can expect lower temperatures, the average highest temperature is around 40.6 ℃ (105.08 ℉). The average rainfall is 13.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 13:14 (hours and minutes), in the middle of the month 13:34 and at the end of the month 13:49.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in June is this: The average highest temperature in India in June is 40.5 ℃ (104.9 ℉). The average lowest temperature is 28.8 ℃ (83.84 ℉). At the beginning of June you can expect higher temperatures, the average highest temperature is around 40.6 ℃ (105.08 ℉). At the end of June you can expect lower temperatures, the average highest temperature is around 38.1 ℃ (100.58 ℉). The average rainfall is 65.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 13:49 (hours and minutes), in the middle of the month 13:56 and at the end of the month 13:56.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in July is this: The average highest temperature in India in July is 35.7 ℃ (96.26 ℉). The average lowest temperature is 27.1 ℃ (80.78 ℉). At the beginning of July you can expect higher temperatures, the average highest temperature is around 38.1 ℃ (100.58 ℉). At the end of July you can expect lower temperatures, the average highest temperature is around 34.55 ℃ (94.19 ℉). The average rainfall is 203.3 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 13:56 (hours and minutes), in the middle of the month 13:48 and at the end of the month 13:33.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in August is this: The average highest temperature in India in August is 33.4 ℃ (92.12 ℉). The average lowest temperature is 26 ℃ (78.8 ℉). At the beginning of August you can expect higher temperatures, the average highest temperature is around 34.55 ℃ (94.19 ℉). At the end of August you can expect higher temperatures, the average highest temperature is around 34 ℃ (93.2 ℉). The average rainfall is 210.8 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 13:33 (hours and minutes), in the middle of the month 13:13 and at the end of the month 12:50.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in September is this: The average highest temperature in India in September is 34.6 ℃ (94.28 ℉). The average lowest temperature is 24.7 ℃ (76.46 ℉). At the beginning of September you can expect lower temperatures, the average highest temperature is around 34 ℃ (93.2 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 34.1 ℃ (93.38 ℉). The average rainfall is 132 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:50 (hours and minutes), in the middle of the month 12:25 and at the end of the month 12:00.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in October is this: The average highest temperature in India in October is 33.6 ℃ (92.48 ℉). The average lowest temperature is 19.1 ℃ (66.38 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 34.1 ℃ (93.38 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 30.85 ℃ (87.53 ℉). The average rainfall is 20.6 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:00 (hours and minutes), in the middle of the month 11:34 and at the end of the month 11:10.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in November is this: The average highest temperature in India in November is 28.1 ℃ (82.58 ℉). The average lowest temperature is 12.8 ℃ (55.04 ℉). At the beginning of November you can expect higher temperatures, the average highest temperature is around 30.85 ℃ (87.53 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 25.65 ℃ (78.17 ℉). The average rainfall is 3.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:10 (hours and minutes), in the middle of the month 10:49 and at the end of the month 10:31.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in India in December is this: The average highest temperature in India in December is 23.2 ℃ (73.76 ℉). The average lowest temperature is 8.8 ℃ (47.84 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 25.65 ℃ (78.17 ℉). At the end of December you can expect lower temperatures, the average highest temperature is around 22.25 ℃ (72.05 ℉). The average rainfall is 9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 10:31 (hours and minutes), in the middle of the month 10:21 and at the end of the month 10:19.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.