Could we feel a jetlag-equivalent effect when we travel a long distance in the North-South direction? We would be moving from summer to winter in one day. Doesn't this affect our biological clocks?

  • Possibly jet lag is being confused with a nervous system condition typified by sleep disorders, tiredness, apathy, etc
    – Gayot Fow
    Apr 4, 2016 at 3:46
  • @GayotFow: It's "jet lag", not jet lag. I mean some equivalent disturbance, caused by shifting too fast from environment.
    – Pierre B
    Apr 4, 2016 at 11:40

3 Answers 3


Maybe you won't have jet lag but still there might be problems.

If it's a redeye then you will miss a good night's sleep.

Say FRA-CPT is easily 12 hours during which you will mostly be sitting in a dry, pressurized aluminium tube with limited mobility. If you doze off a bit it might upset your sleep schedule, depending. Also, you might just find the whole experience just exhausting.

So: jetlag no but you still might need a day to recover.

  • 1
    But the long flight fatigue applies no matter where you're going
    – blackbird
    Apr 4, 2016 at 0:51
  • 2
    That's basically my answer condensed: if it's a long flight, it's fatiguing.
    – user4188
    Apr 4, 2016 at 1:22
  • If it's a redeye then you might miss a good night's sleep. The only time I ever did this was to spend February in South Africa when I was living in Amsterdam. The flight down was overnight. I slept for six or seven hours, not terribly comfortably, but it was good sleep nonetheless. I worked the next day without needing any time to recover.
    – phoog
    Apr 4, 2016 at 5:57

There's no jetlag when you're travelling within the same timezone (or +/- 1 hour) in a north-south axis.

For other effects it depends a lot on your constitution and physical fitness, for some even a minor change in climate is felt very strongly for others not at all. I travelled to Argentina from a North American winter, from -20 to +35 and I didn't get sick, my girlfriend on the other hand recently got home sick after a trip to Peru. So it depends

Change of temperature alone probably won't affect your internal clock, you have to look at altitude, humidity, time difference and exposure to daylight among other factors to get a better idea of how a trip might affect you.


Can you get "jetlag", not really because there is no major time change.

BUT depending on how far south you started and how far north you are going and what time of year it is, your body's clock can be upset because of differences in sunrise and sunset.

As an example, in summer or winter if you flew between South Africa and Norway you would go from a short day to almost 24 hours of daylight. And since sun plays a role in our body clock, you would have some disruptions to your sleep patterns. But if you made the same trip in spring or fall, then the sun differences would be more minor.

  • I flew once from Amsterdam to Johannesburg in early February. I returned in early March, and three days later I was in Oslo. I did not experience any of the effects you suggest. (On the other hand, I found jet lag in the Amsterdam winter or summer, after returning from North America, to be devastating because of the lack or abundance of daylight.) Do you have any evidence to support this answer?
    – phoog
    Apr 4, 2016 at 6:04
  • For starters each person reacts differently to time / daylight changes, so the phoog effect does not equate to other people's effects. Second your trip from Jo'burg to Oslo fell into spring, which I mentioned had only minor differences. Third, my statement comes from many years of flying from places with 10 hours of daylight to places with 20+ hours of daylight and its effects on sleep patterns (both mine and the hundreds of customers I have led on tours).
    – user13044
    Apr 4, 2016 at 7:20
  • I'm not sure it was late enough in the spring for the differences to be minor; in early March the sunset is roughly 12h45 after the the sunrise in Cape Town, and roughly 10h30 in Oslo (though it was so dreary when I first got to Oslo that it seemed that the day length was shorter than in Amsterdam in December). So the change in day length was 2h15. I don't know if you consider that minor, but I suspect 20 hours of sunlight would disrupt my sleep with or without travel from a dark place. Anyway, I was mainly asking for your source, which appears to be personal experience; thanks for clarifying.
    – phoog
    Apr 13, 2016 at 14:30

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