"Lit" is a pun, and the poem plays on both meanings. To be lit is to be drunk, and it also suggests something burning or brightly illuminated. The speaker starts the day with gin, and by afternoon there is heat and ice, two opposites sitting side by side. That small detail hints at a day that has slipped a little out of order.
Then comes the strange turn. The speaker sees a well and prepares to row, as if it were a lake or a river. Rowing a well makes no practical sense, which is the point: the drink has loosened the speaker's grip on ordinary logic, and the mind has set off on its own little voyage. A well is deep, narrow and dark, so the image might also suggest something sinking inward.
The mood is dreamy, woozy and quietly comic, with a faint note of loneliness. The speaker doesn't seem alarmed, just calmly ready to set out. Judging by the poem's brevity, the effect is of a sudden, odd flash of vision rather than a story.