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Spring is one of the four seasons of the temperate zones, the transition from winter into summer.

There are different views on when the season starts and finishes.

The Merriam-Webster dictionary states that spring comprises "in the northern hemisphere usually the months of March, April, May, or as reckoned astronomically extending from the vernal equinox (March 21) to the June solstice (June 21)."

Chambers 21st Century Dictionary states that spring is "the season between winter and summer, when most plants begin to grow, and usually thought of in the N hemisphere as consisting of the months from March to May inclusive, and in the S hemisphere as September to November".[1]

The UK Met Office also considers that spring consists of the months of March, April and May.[2].

The Oxford English Dictionary says that spring is "in the N. hemisphere from March to May and in the S. hemisphere from September to November".

Cambridge Advanced Learner's Dictionary considers that spring lasts "from March to June north of the equator, and from September to December south of the equator".[3]

As in summer, the axis of the Earth is tilted toward the Sun, and the length of daylight hours rapidly increases as latitude increases. The hemisphere begins to warm significantly, causing new plant growth to "spring forth", giving the season its name (see Effect of sun angle on climate). Snow begins to melt, and rivers and streams swell with runoff and spring rains. Most flowering plants bloom this time of year, in a long succession 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 see "spring" at all until May or even June, or December in the outer Antarctic.

Dandelion in spring

Severe weather most often occurs during the spring, when warm air begins to invade from lower latitudes while cold air is still pushing from the polar regions. Flooding is also most common in and near mountainous areas during this time of year due to snowmelt, many times accelerated by warm rains. In the United States, Tornado Alley is most active by far this time of year, especially since the Rocky Mountains prevent the surging hot and cold air masses from spreading eastward and instead force them directly at each other. Besides tornadoes, supercell thunderstorms can also produce dangerously large hail and very high winds, for which a severe thunderstorm warning or even tornado warning is usually issued. Often, spring storms trigger dozens of warnings, one right after the other, often simultaneously along a line hundreds of miles or kilometers long. Even more so than winter, the jet streams play an important role in severe weather in the Springtime.

The hurricane season officially begins in late spring, on May 15 in the northeastern Pacific, and June 1 in the northern Atlantic. Before these dates, hurricanes are almost unheard of and even tropical storms are rare, one of the earliest ever being Tropical Storm Ana in mid-April 2003. Even in June, hurricanes are uncommon, as 21 of June's days are spring.

Springtime is seen as a time of growth, renewal, of new life (both plant and animal) being born, and of the cycle of life once again starting. It is also used more generally as the start of better times, as in Prague Spring.

Temperate seasons
Spring	Summer	Autumn/Fall	Winter
Tropical climate seasons
Wet season		Dry season