Spring Spring begins in the northern hemisphere around the months of March, April, May, or as reckoned astronomically extending from the vernal equinox. As in summer, the axis of the Earth is tilted toward the Sun and the length of daylight rapidly increases. The northern hemisphere begins to warm significantly causing new plant growth to "spring forth," giving the season its name. Snow begins to melt and streams swell with runoff and spring rains. Most flowering plants bloom this time of year, in a long succession sometimes beginning even when snow is still on the ground, and continuing into early summer. In normally snowless areas "spring" may begin as early as February during warmer years, with subtropical areas having very subtle differences, and tropical ones none at all. Subarctic areas may not experience "spring" at all until May or even June, or December in the outer Antarctic. Severe weather most often occurs durin