The poet Robert Browning wrote those words while in Italy, where all was warm and bright. For most of the Northern Hemisphere above 40 degrees latitude, particularly in Vermont, April 1 usually gray and cold and muddy. The daffodils and crocuses are tentatively poking up from the ground, the trees haven't yet budded and the migrating birds are just starting to straggle back north.
Winter may be finished, but spring has yet to fully arrive. Browning, whose poetry we're reading today, never saw a Vermont spring, which is slow to come and quick to leave.