I am taking a Carnival cruise on Dec. 4th, we live in Illinois. Should we go to Miami the day before?

Or, should we risk going the day of? The boat leaves the dock at 4pm. It takes 3 hours to fly from Chicago & it is the 1st week of December in Illinois. Usually we don't have much snow by then, but should we risk it or go the day before just in case? We will be cruising on the Carnival Valor to Grand Cayman, Belize, Isla Roatan & Cozumel.