Judith Wright's poem "Hunting Snake" tells of a couple who freeze to watch as a "great black snake" slithers by them. Frozen by his presence, the couple stands still as they contemplate the snake, his path, and his departure. 

The word "gentlest" appears in line two: "under the autumn’s gentlest sky." Here, the word gentlest conveys, or suggests, a calm and peaceful sky and scene. Since weather can define how things go on the surface of the earth (for example, if stormy, humans and animals run for cover), the gentle sky illustrates the calmness of the day and the inhabitants of the earth. Contrasting this image, as soon as the snake appears, the couple's peace is shattered. 

The word "grace" appears in the first line of the poem: "Sun-warmed in this late season’s grace." Here, the term grace refers to the approval of the season (personification). One can assume that it is the end of either winter or fall, and the warmth of the sun is the one thing which allows the couple the ability to stroll outdoors. The season's grace refers to the season's approval.