North India has two main climatic zones: the upper reaches of India that is home to Himalayas with its foothills, making for a deciduous, cold and dry climate and the hinterland that is landlocked and makes up for a continental type of climate. The Himalayan region is best visited in summers, i.e. between March to May, while the proper North India or the hinterland as they call it in India, is best visited during winter and early summer (between October to April). The weather in North India during most other months is quite endurable, except peak of summers in hinterland and peak of winters in Himalayas. 

We shall comment in detail upon each season in both, the Himalayas as well as the hinterland of North India below.

Himalayas: 

The northern reaches of North India including Himalayas and Garhwal region of foothills become ideal tourist attractions during summer to escape the heat from plains. In places like Jammu-Kashmir, Leh-Ladakh and hill stations like Shimla, Kullu, Manali (Himachal Pradesh) as well as the many pilgrims of Uttarakhand, the temperature ranges from 13-19°C. This time becomes one of the best seasons to enjoy the hill stations.

Hinterland:

The landlocked hinterland like Delhi, Agra, Amritsar etc experience a hot summer, mostly dry, with average temperature of 40°C. Until April these places are still worth visiting but May is the hottest and heatstrokes are very common. Rajasthani cities like Jaipur, Udaipur, Jodhpur etc are hotter than the other hinterland cities, as desert sands heat up like the furnace. The dry heat here is very oppresive and dehydration, diarrhoea etc are very common.

Himalayas: 

Heavy rainfall is experienced in this region between July to September. Some upper reaches of Kashmir and Ladakh are exempted from this heavy rainfall but they are compensated during the heavy snowfall of winter. Many roadways get shut down due to landslides and you will need to check your destination in detail if travelling in this season. 

Hinterland:

Rains bring relief to the hinterland of India, also constituting a major part of the populace’s joy as farms bloom and a good rainy season makes for a year of surplus grain. Rainfall is brought by the South West Monsoon Winds and follows through late June, July, August and most of September. Rajasthan is perpetually a desert state and hence receives very less precipitation, especially in the Thar area of Jodhpur and Jaisalmer. While this may not be the best time to visit most destinations here, the month of August is great for Mathura-Vrindavan to partake in the grandeur of the festival of Janmashtami (birth of Lord Krishna).

Himalayas:

Winter in the mountains are cold, obviously, but they are also white and utterly gorgeous. With every 1000 m of ascent, there is a temperature drop of 6.5°C. Hence most of Kashmir, Ladakh, and Himachal come under snowfall. The lower Garhwal regions of Himachal and Uttarakhand come to freezing point but are still accessible. February is the coldest month in most areas. 

Hinterland:

The season of winter makes for some great opportunity for tourism in the hinterland as the temperatures fall to a pleasant 8-20°C in most areas. Places like Delhi, Punjab, Rajasthan, Mathura are cold and dry and you need one layer of warm clothes to get by. But the sun is always high and the weather is pleasant. The Taj Mahal is best visited on winter afternoons and Holi festival (February-March) should be celebrated in Mathura-Vrindavan belt. Rajasthan is also quite cold through the winters and the festival of Diwali in October-November makes for some extra special touristy in cities like Jaipur, Udaipur and Nathdwara town. The New Year’s Eve is best celebrated in the desert camps of Thar (Jaisalmer), under the stars, with local music and food to accompany. 

Hence winter is the best season to visit the hinterland of North India, while summers become ideal for Himalayan tours.