The cruise season in Antarctica begins in October and lasts through March. During Antarctica's winter, the waters surrounding the peninsula are like one huge block of ice, impeding travel to and from the area. Temperatures, even those along the coastline, drop well below zero. Travel during this time is virtually impossible, which is why Antarctica cruises only operate during the Southern Hemisphere's late spring and summer, when temperatures are much warmer and animals, such as penguins, birds, whales and seals, are active in the area.
Many cruises depart from Ushuaia, which has a milder climate, but as you travel south to the Antarctic Peninsula, temperatures will quickly drop into the 20s and 30s. You'll need to be prepared with a waterproof parka, a hat and gloves, among other cold-weather gear, as well as your camera and a sense of adventure.
The prime time for Antarctica exploration is in December and January when the continent experiences the longest hours of daylight, lasting up to 20 hours a day. This is generally also the best time for viewing the largest selection of wildlife. However, earlier in the season--in November as the pack ice is breaking up--you'll be just in time to see all sorts of birds, especially penguins as they court and mate, and the pristine scenery is at its best. You'll also have the greatest chance of spotting seals, lounging on pack ice and shorelines, although some areas of the continent may still be inaccessible due to ice.
As the austral summer winds down in late February and March, you'll see a decrease in the number of visitors, which means less waiting for zodiacs and station tours. These months also mark the period of time when penguin chicks are beginning to fledge and adult penguins are ashore molting. Additionally, the greatest number of whales will be frolicking in the icy blue waters of the Southern Ocean.