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Spring Flowers: Tulips - © Calendar Updates

United States
Holidays

Administrative Professionals Day

April Fools' Day

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Ash Wednesday

Autumn

National Boss Day

Christmas Day

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秒速赛车官方网站 Cinco de Mayo

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秒速赛车官方网站 Daylight Saving Time

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秒速赛车官方网站 Mardi Gras

秒速赛车官方网站 Memorial Day

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秒速赛车官方网站 Mother's Day

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秒速赛车官方网站 Summer

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秒速赛车官方网站 National Teacher Day

Thanksgiving Day

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Winter

 

In the United States and the rest of the northern hemisphere, the first day of the spring season is the day of the year when the Sun crosses the celestial equator moving northward (on March 20th or 21st). This day is known as the Vernal Equinox秒速赛车官方网站.

A common misconception is that the earth is further from the sun in winter than in summer. Actually, the Earth is closest to the sun in December which is winter in the Northern hemisphere.

As the Earth travels around the Sun in its orbit, the north-south position of the Sun changes over the course of the year because of the changing orientation of the Earth's tilted rotation axes. The dates of maximum tilt of the Earth's equator correspond to the Summer Solstice and Winter Solstice, and the dates of zero tilt to the Vernal Equinox and Autumnal Equinox.

 

 

The reason for these changes has to do with the Earth's yearly trip around the sun. For part of the year the Earth's North Pole points away from the sun and part of the time toward it. This is what causes our seasons. When the North Pole points toward the sun, the sun's rays hit the northern half of the world more directly. That means it is warmer and we have summer.

The declination of the Sun on the vernal equinox is 0° 00'。 On the day of the vernal equinox, day and night are nearly the same amounts of time。 In the United States, there are about 12 hours of daylight on this day。

 

Tornado Season


March is the traditional start of tornado season in the United States. Although tornadoes can occur at any time throughout the year, the peak activity period is March through early July, according to the National Weather Service (NWS).

An average of 1,200 tornadoes touch down in the United States each year, and most of them form during this tornado season. Because these storms kill about 70 Americans annually and injure some 1,500 others, disaster experts urge families to be prepared — particularly those who live in Tornado Alley.

Tornado Alley is roughly defined as the area of the Central Plains from Texas to Nebraska。 This is where most tornadoes form each season。 Much of the damage that tornadoes inflict each year occurs in this region of the country。 Texas has the highest number of tornadoes, with an average of 124 each year。

 

Tornado Map

Tornado map courtesy U. S. Geological Survey

 

 

 

Links

 

- Ready.gov is a national public service advertising (PSA) campaign designed to educate and empower Americans to prepare for and respond to emergencies including natural and man-made disasters. The goal of the campaign is to get the public involved and ultimately to increase the level of basic preparedness across the nation.

 

- Through the Naval Oceanography Portal, the United States Naval Observatory provides astronomical information on the Earth's orbit around the Sun and how it relates to the changing seasons.

 

(American Red Cross)

 
 
 

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