This is the 335th most frequent Swedish word.
södra
"Southern."
In this sentence, "södra" is used as an adjective modifying "delen", specifying "the southern part".
Vi bor i den södra delen av staden.
We live in the southern part of the city.
Here, "södra" describes "vinden", indicating "the wind coming from the south".
Den södra vinden förde med sig varma luftmassor.
The southern wind brought warm air masses with it.
In this usage, "södra" designates the southern region of Sweden as an identifying attribute.