Spring (late March to May) and autumn (October to November) are the finest, with cherry blossom or fiery maple leaves in the park and mild, comfortable days. Summer is hot and humid, and the June to October period can bring typhoons, while winter is cold but clear and quiet, and the deer look especially striking against frost or the rare dusting of snow.
The park deer are wild animals, not pets, and can bite, head-butt or kick, especially when they smell food. Keep crackers hidden until you are ready, feed quickly and calmly, show open empty hands when you have none left, and watch small children closely around them.
Nara summers are hot and humid, and much of the park and temple grounds are open and shadeless. Carry water, use the shaded halls and museums in the midday heat, and plan the open sights like the park and Mount Wakakusa for early morning or late afternoon.
The wider June to October season can bring heavy rain and occasional typhoons that disrupt trains and close outdoor sites. Check the forecast and rail updates on those days, keep a flexible plan, and have an indoor museum or temple hall as a wet-weather alternative.