"In the Southern Hemisphere, New Year’s is in summer, unlike in Japan!"
"In the Southern Hemisphere, New Year’s is in summer, unlike in Japan!"
"It’s summer during New Year’s in the Southern Hemisphere, which is the opposite of Japan."
"In the Southern Hemisphere, it’s summer around New Year’s, right?"
「南半球では、日本と逆で正月は夏ですね!」は英語では、
**南半球(the Southern Hemisphere)+ 夏(summer)+ 日本と逆(unlike / the opposite of Japan)**
を組み合わせて表現します。