Winter: (Mid -October to March) is the best time to visit North India, as it offers the best weather and most comfortable temperatures to experience prime attractions of the region in the best way.
Summer: Kashmir is the ideal destination In North India for Summer travel as the weather is quite pleasant during the summer months of April to September. The orchards and meadows are in full bloom, you can opt for activities such as cliff climbing and trekking.
The Himalayan region of Uttarakhand and Himachal Pradesh are round-the-year destinations as the climate is very moderate during summers; the peak winter months can see snow in the region. Both these regions are blessed with views of majestic mountains, emerald-green valleys, and mighty rivers.
The plains of North India (Delhi, Agra and Rajasthan region) see the best weather in the winter months (Oct to Mar), The Summers in plains face harsh heat, sometimes the temperatures can soar 48 degrees in the day.
Monsoon: The monsoon arrives in most parts of North India from mid-June onwards and lasts till mid-September; rainfall in most parts of North India works as your friend as the showers bring a drop in the temperatures. July and August are the wettest months, but September has light showers, so it is a great time to visit Rajasthan.
Ayurveda practice is the best during these months, as the body responds better to treatments, making it the perfect time to head out for a wellness retreat.
Delhi/Agra region can see thick fog around Christmas/NYE period and the visibility might be hampered during the early mornings and also around dusk, it is best advised to start sightseeing after 9/10 AM during this time of the year.
Overall, October, November and February are the best months to visit weather-wise.