The best time of the year to visit Nagpur is from October up until February, which is the winter season. During this time the temperature remains much lower than the rest of the year, which is conducive to sightseeing. The temperature can drop significantly, making it bearable during the day and cooler in the evenings, so make sure you pack accordingly.
You can also come during the summer, which is from March until June. The temperature in this area get extremely high and this is the worse time to come and visit because the heat is unbearable. However, it is possible to visit, but not advised.Also, between July and September is when the monsoon hits the area, which means heavy rains that will last for days on end. The rains make it hard to do any sightseeing or even any activities outside, so try to avoid this time as well. However, you can come and visit during this time if you don't plan on doing any of the outdoor activities.