I've seen Saying Mashiv HaRuach in the Southern Hemisphere. Similarly, is Birkas Ha'ilanos (ברכת האילנות) said in Tishrei in the southern hemisphere? That's when the trees bloom.
The Ritva writes (Rosh Hashana 11a):
ויומי ניסן לאו דוקא אלא כל מקום ומקום לפי מה שהוא דמלבלבי.
"The days of Nissan" is not precise, but rather every place according to when the trees bud.
Based on this, Rabbis Yitzchok Yaakov Weiss (Minchat Yitzchak 10:16) and Tzvi Pesach Frank (Har Tzvi OC 118) ruled that in the Southern Hemisphere the blessing should be recited in Tishrei/Cheshvan when the local trees actually start budding.