Antarctica is only accessible during the austral summer, roughly November through March. Outside this window the continent is locked in by sea ice, plunged into 24-hour darkness, and battered by temperatures that make human travel impossible. Every expedition cruise, every fly-in trip, every tourist visit happens in this narrow five-month window.
Early season, from November to mid-December, brings pristine snowscapes and the start of penguin courtship — colonies are noisy, active, and photogenic. The ice is still breaking up, so some landing sites may not yet be accessible, but the snow cover is dramatic and untouched. This is also when you'll see the most icebergs calving. Mid-season, from late December through January, offers the warmest temperatures (hovering around zero Celsius on the Peninsula), the longest daylight hours, and the widest range of accessible landing sites. Penguin chicks are hatching, and seal pups appear on the beaches. It's peak season and the most popular time to visit.
Late season, from February into early March, is prime time for whale watching. Humpbacks and minkes feed in large numbers in the nutrient-rich waters, and you'll often see them from the ship and the zodiacs. Penguin chicks are growing fast and molting into their adult plumage — endearingly scruffy. The days start getting shorter and temperatures drop, but the wildlife spectacle is at its richest. Some operators offer discounted late-season departures.
Whenever you go, expect 24-hour daylight or near-daylight. The sun barely sets in December and January, which is disorienting and wonderful. Bring an eye mask if you need darkness to sleep. Weather on the Antarctic Peninsula is notoriously changeable — you can experience all four seasons in a single afternoon — so dress in layers and keep your expectations flexible. The one certainty is that no two days will look the same.