Hi Prajkta, November to April is the best time to visit Kaziranga National Park, a lot of migratory birds visit the park during this time as well. The rain is minimum during this time, for rest of the year the weather is hot and humid.
Kaziranga experiences tropical climate; thus the best time to visit for a wildlife tour would be either Summer or Winters. During the summer season, it is very hot and humid during the day but the night remains mild. One should avoid visiting here during the monsoon season as this is when the water of the Brahmaputra River floods the park. Also, the park remains closed for visitors from 1st May to 31st October.
Kaziranga National Park is starts from October to till April but best time to visit from October to January. There are 4 Zones In Kaziranga National Park like western, central and eastern and burapahar Zone. For more information, kindly visit website: http://kazirangatourism.in/online-kaziranga-safari-booking.php