The role of nature, seasons and climate is to promote the challenges that the postman needs to overcome.
We can arrive at this answer because:
"The postmaster" shows the daily life of a postman, his difficulties, and his joys with this working uncle.
As we know, a postman has to face many difficulties to complete his deliveries and one of these difficulties is related to nature.
This is because nature, seasons, and weather can make it difficult for the postman to arrive at his final destination, as it can promote difficult terrain to walk and very cold or very hot climates.
In this case, we can say that nature, seasons, and weather have a very strong impact on the story, as it interacts directly with the postman and his goals.
