Traveling South This Winter? A Health Checklist for Southern Hemisphere Summer Trips (Dec-Feb)

If you're leaving a Northern Hemisphere December for Patagonia, New Zealand, Australia, or an Antarctica cruise, you're trading your own winter for someone else's summer, and the health planning that matters shifts accordingly. Southern Hemisphere flu season runs April through September, according to the CDC, meaning a December-to-February trip actually lands outside the peak respiratory illness window down south. What replaces it as the bigger planning concern: altitude if your itinerary includes Patagonian trekking routes or Andean crossings, motion sickness if you're booked on a Drake Passage crossing to Antarctica, and the same traveler's diarrhea risk that applies to warm-weather travel anywhere. Start your visit on Wandr and get a plan built around what this specific trip window actually calls for, not a generic packing list.

Why the Season You're Traveling In Isn't the Season at Your Destination

This trips up more travelers than you'd expect. Someone leaving a Chicago or Toronto winter assumes they're escaping flu season entirely, which is only half true. You're leaving your own hemisphere's flu season, but the Southern Hemisphere runs on the opposite calendar, April through September per the CDC, so December through February actually falls in its lower-transmission stretch. The practical upside is real: respiratory illness risk during a Dec-Feb Southern Hemisphere trip tends to be lower than at other times of year there. It doesn't mean zero risk, and routine vaccines (including an annual flu shot) are still worth being current on for general protection, but it does mean this specific window isn't the one to build your health planning around respiratory illness.

Patagonia and High-Altitude Trekking Season

December through February is peak trekking season in Patagonia, when routes like Torres del Paine in Chile and the areas around El Calafate and El Chaltén in Argentina see the most visitors, and it's also when Andean crossings and higher-elevation itineraries are most commonly booked. The CDC Yellow Book defines altitude illness risk as starting at sleeping altitudes around 2,450 m (8,000 ft), with acute mountain sickness affecting roughly 25% of visitors sleeping above that elevation in comparable high-altitude regions. Most classic Patagonia trekking stays below that threshold, but itineraries that add a high mountain pass, a volcano ascent, or an extension into higher Andean elevations elsewhere in South America can cross it. If your specific route includes meaningful elevation gain, acetazolamide taken starting the day before ascent can compress the usual multi-day acclimatization window down to about a day. This is exactly the kind of itinerary-specific detail our providers sort out during a Wandr visit rather than something to guess at from a packing list.

Antarctica Cruises and the Drake Passage

Antarctica's cruise season runs roughly November through March, aligning almost exactly with this Dec-Feb window, and most voyages depart from Ushuaia, Argentina, crossing the Drake Passage to reach the Antarctic Peninsula. The CDC Yellow Book notes that seasickness affects up to 25% of travelers on ship crossings even with modern stabilizer systems, and the Drake Passage has a well-earned reputation among sailors for rough water. Motion sickness medication is worth having sorted out before you board, not something to improvise once you're already feeling it. Depending on your history with motion sickness and the specifics of your crossing, our providers can discuss whether meclizine or scopolamine fits your situation better.

Traveler's Diarrhea Doesn't Take a Season Off

Warm-weather travel to South America, Australia, and parts of the South Pacific carries the same baseline traveler's diarrhea risk as anywhere else, and summer heat can actually raise the risk somewhat since food safety practices matter more when ambient temperatures climb. CDC data puts attack rates for traveler's diarrhea at 30% to 70% of travelers over a two-week period depending on destination and season, with bacteria responsible for the large majority of cases. A self-treatment antibiotic, prescribed before you leave, means you're not trying to find and evaluate a pharmacy in an unfamiliar country if symptoms show up mid-trip.

Building Your Dec-Feb Southern Hemisphere Checklist

Confirm whether your specific route crosses 8,000 feet. Classic lowland Patagonia stays below the altitude illness threshold, but check any add-on treks, passes, or extensions specifically rather than assuming based on the region's general reputation.

Sort out motion sickness medication before an Antarctica or Patagonian fjord crossing, not during it. Once you're feeling seasick, it's harder to keep any medication down, which is exactly why this is worth arranging in advance.

Pack a self-treatment antibiotic for traveler's diarrhea regardless of season. Warm-weather travel doesn't reduce this risk, and summer conditions can make food safety lapses somewhat more likely.

Don't skip routine vaccines just because it's not Southern Hemisphere flu season. Staying current on standard vaccines, including your annual flu shot, still matters for your own protection and for the people you're traveling with.

Check destination-specific guidance for wherever you're actually headed. Argentina, Chile, New Zealand, Australia, and South Africa each carry their own specific recommendations beyond this general seasonal checklist.

Frequently Asked Questions

Is flu a bigger risk when traveling to the Southern Hemisphere in December? Not during this specific window. Southern Hemisphere flu season runs April through September per the CDC, so a December-to-February trip falls outside the peak transmission period there. Staying current on your annual flu vaccine is still worthwhile for general protection, but this isn't the trip type to build extra planning around respiratory illness.

Do I need altitude sickness medication for a standard Patagonia trip? It depends on your specific itinerary. Classic lowland routes around El Calafate and much of Torres del Paine stay below the roughly 8,000-foot threshold where altitude illness risk begins. Itineraries that add higher passes or Andean extensions may cross it. Our providers can review your specific route.

What should I pack for an Antarctica cruise's Drake Passage crossing? Motion sickness medication arranged before departure is the main travel-medicine consideration specific to this route, since seasickness affects up to 25% of cruise travelers even with modern stabilizers, according to the CDC Yellow Book. Options like meclizine or scopolamine are worth discussing with our providers based on your motion sickness history.

Is traveler's diarrhea risk different in summer versus winter at these destinations? The underlying risk from contaminated food and water exists year-round, and warmer summer conditions can modestly increase it if food safety practices lapse. A self-treatment antibiotic is worth having regardless of which season you're traveling in.

When does Antarctica cruise season run? Roughly November through March, which overlaps closely with the December-to-February window many Northern Hemisphere travelers choose specifically to escape winter at home. Most voyages depart from Ushuaia, Argentina.

Do I still need any vaccines if I'm traveling during the Southern Hemisphere's lower-flu-transmission months? Yes. Being outside peak flu season there doesn't change other destination-specific vaccine recommendations, which depend on the country, region, and activities on your itinerary rather than the calendar month alone.

Sources

1. Centers for Disease Control and Prevention. CDC Tracks Ongoing Flu Activity in the Southern Hemisphere. https://www.cdc.gov/flu/spotlights/2022-2023/ongoing-flu-southern-hemisphere.htm
2. Centers for Disease Control and Prevention. High-Altitude Travel and Altitude Illness. CDC Yellow Book. https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html
3. Centers for Disease Control and Prevention. Cruise Ship Travel. CDC Yellow Book. https://www.cdc.gov/yellow-book/hcp/travel-air-sea/cruise-ship-travel.html
4. Centers for Disease Control and Prevention. Travelers' Diarrhea. CDC Yellow Book. https://www.cdc.gov/yellow-book/hcp/preparing-international-travelers/travelers-diarrhea.html

Related Reading

For destination-specific guidance on where you're actually headed, see our travel health guides for Argentina, Chile, New Zealand, Australia, and South Africa.

Medical Disclaimer

This article is for general educational purposes and does not replace individualized medical advice. Health needs vary by exact itinerary, activities, and individual health history. Our providers review your health profile before prescribing anything.

Start your visit on Wandr and get a plan built for your specific Southern Hemisphere itinerary (see /destination-check)