This is the 14722nd most frequent Polish word.
północnych
"Of the north" or "northern."
Here, "północnych" functions as an adjective describing "forests" (northern).
Spotykamy się w lasach północnych.
We are meeting in the northern forests.
In this context, "północnych" qualifies "regions" and indicates their geographical orientation.
Ludy północnych regionów były znane ze swoich tradycji.
The peoples of the northern regions were known for their traditions.
"Północnych" here modifies "areas," specifying their relative position in terms of latitude.