In 2009, spring fell on March 20th in the Northern Hemisphere.
Spring Day is a holiday marking the coming of the spring season, which takes place in different countries, on varying dates. Snow, if a normal part of winter, begins to melt and streams swell with runoff. Frosts, if a normal part of winter, become less severe. Many temperate climates have no snow and may have no frosts, and the air and ground temperature increase. Many flowering plants bloom this time of year, in a long succession sometimes beginning even if snow is still on the ground, continuing into early summer. Unstable weather may more often occur during spring, when warm air begins on occasions to invade from lower latitudes, while cold air is still pushing on occasions from the Polar Regions. Flooding is also most common in and near mountainous areas during this time of year because of snowmelt, many times accelerated by warm rains.
