“They need to be out by the sixth of February,” Dr Pearce said, when winter sets in and temperatures drop another 40 degrees Centigrade.
I doubt the temp drops by 40C on a particular day every year.
Maybe he means when that area BEGINS its 40C plunge. Even though it is officially summer in the Antarctic, the sun has been getting lower on the horizon since Dec. 21. Right now it is getting colder and COLDER.
This year, due to global warming/climate change, the temperature rose by 40 degrees and they had to swim out.