What is the best time of year to travel to Antarctica?

The Australian Antarctic Division puts the average annual temperature on the Antarctic coast at about 14°F (−10°C), with summer readings on the coast able to exceed 50°F (10°C) and winter readings falling below −40°F (−40°C). Move inland and up and the numbers collapse: the elevated interior reaches about −22°F (−30°C) in summer and can drop below −112°F (−80°C) in winter. The lowest surface temperature ever recorded on Earth, −128.6°F (−89.2°C), was logged at Vostok station on 21 July 1983. Nobody visits in July.

Antarctica is also a desert, which matters for what a summer day actually looks like. Continent-wide precipitation averages about 5.9 inches (150 mm) of water equivalent per year. The elevated plateau gets under 2.0 inches (50 mm). The coast generally gets more than 7.9 inches (200 mm), and one area near the Bellingshausen Sea exceeds 39 inches (1,000 mm) — which is why the maritime fringe is the wet, cloudy, changeable part of the continent.

Summer is also when the rules bite. The Antarctic Treaty Consultative Meeting's Resolution X of 2011 sets out the General Guidelines for Visitors to the Antarctic, and three of its provisions shape every itinerary: no more than 100 passengers may be ashore from a vessel at one time unless site-specific advice sets a lower figure, landings should keep a 1:20 ratio of guides to passengers, and vessels carrying more than 500 passengers may not land at all.

The Division notes that cloudy conditions are more common near the coast, and particularly over the Antarctic Peninsula — so the Peninsula summer is less the hard blue glare of the polar plateau than a grey-and-white maritime one, with weather arriving off the Southern Ocean rather than draining off the ice sheet.

The 500-passenger landing bar is the single most consequential line in the guidelines for anyone comparing trips. A large vessel can carry you through the Peninsula's channels and show you everything from the rail, and never put you on land. The 100-ashore cap does the same thing more quietly on mid-sized ships: time ashore is rationed in rotations, so a long day at a site is a shorter day per person than the schedule suggests.

• Before you book — Check which of the 32 sites with published visitor guidelines your route includes; those documents, not the brochure, set how many people can stand where.
• On the ship — The guidelines require operators to supply every visitor with a copy, and to carry a sufficient number of trained, experienced guides. Ask for both.
• Ashore — Boots and gear must be washed before arrival and cleaned again between sites, because nothing living may be introduced to the continent.

The Antarctic Conservation Act reaches every US citizen bound for Antarctica, whether or not they travel with the US Antarctic Program, and every Antarctic expedition originating in the United States. Without a permit it is prohibited to take native mammals or birds, cause harmful interference, enter an Antarctic Specially Protected Area, introduce a species, or discharge designated waste; penalties run to about $34,457 and 1 year of imprisonment per violation, under implementing regulations at 45 CFR Part 670 and Part 671. Permit applications take roughly 45 to 60 days to process and include a 30-day public comment period after a Federal Register summary appears, so anything beyond ordinary sightseeing has to be started months out. The Division's own guidance is blunt about the rest: do not expect a rescue service, and do not walk onto glaciers or large snowfields without the equipment and experience for it.

The wildlife question in this chapter covers when penguins and whales are actually present, which is the other half of choosing a departure date.