Which route? I went in December last year the machame route. Be prepared for a variety of conditions. We had rain,hail and snow. Always carry a fleece jacket,raingear,gloves and warm hat,not in your porters bag in your bag.
Many people were forced to turn around as they were hiking in shorts and had no warm clothes when it hailed for several hours! Make sure you have a insulation mat that is sufficient,there was 2-3 inches of ice on the ground that night.
This Christmas Patagonia !!!!