First Day of Spring 2018

Today is the Vernal Equinox, the first day of spring in the northern hemisphere. The new season officially begins at 16:15 UTC, which is 12:15 PM Eastern Daylight Time.

Our astronomical seasons are a product of the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the spring months, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.

Since the winter solstice in December, the arc of the sun’s apparent daily passage across the sky has been getting higher and daylight hours have been increasing. Today, the sun appears directly overhead at the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.

As a transitional season, spring is a time when the chill of winter fades away and the warmth of summer gradually returns. The most noticeable increases in average daily temperature, however, usually lag the equinox by a few weeks.

Earth’s solstices and equinoxes. Image Credit: NASA

Groundhog Shadow or Not, Spring has Been Trending Earlier

Today is Groundhog Day, the midpoint of the winter season.

On this day, according to folklore, the weather conditions for the second half of winter can be predicted by the behavior of a prognosticating groundhog. If the groundhog sees its shadow after emerging from its burrow, there will be six more weeks of winter. If it does not see its shadow, then spring will arrive early.

The practice of using animal behavior to predict future weather conditions goes back to ancient times. The particular custom that we are familiar with in the United States grew out of the old world tradition of Candlemas that German settlers brought to Pennsylvania in the 1880s. Today, many communities across the U.S. and Canada continue this age-old ritual with their own special groundhogs.

The most famous of these furry forecasters is Punxsutawney Phil from Pennsylvania – he was portrayed in the 1993 film, “Groundhog Day”. Here in New York City, our local weather-groundhog is Charles G. Hogg. A resident of the Staten Island Zoo, he is more popularly known as “Staten Island Chuck”. This year, the two groundhogs had a difference of opinion. Phil predicts six more weeks of winter and Chuck is calling for an early spring.

But, shadow or no shadow, as the planet warms spring is trending earlier. Below is a look at the temperature trend during the six weeks following Groundhog Day since 1950 in New York City.

Spring is trending earlier as the planet warms. Credit: Climate Central

Perihelion 2018: The Earth is Closest to the Sun Today

The Earth reached its Perihelion today at 5:34 UTC, which is 12:34 AM Eastern Standard Time. This is the point in the planet’s orbit where it comes closest to the Sun.

This annual event is due to the elliptical shape of the Earth’s orbit and the off-centered position of the Sun inside that path. The exact date of the Perihelion differs from year to year, but it’s usually in early January – winter in the northern hemisphere. The Earth will be furthest from the Sun in July.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, the Earth is 147.1 million kilometers (91.4 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) closer than it will be in early July. This position allows the planet to speed up by about one-kilometer per second. As a result, winter in the northern hemisphere is about five days shorter than summer.

The word, perihelion, is Greek for “near sun”.

Earth is closest to the Sun during the northern hemisphere’s winter. Credit: TimeandDate.com

What the Winter Solstice Means

Today is the December solstice, the first day of winter in the northern hemisphere. The new season officially begins at 16:28 UTC, which is 11:28 AM EST.

The astronomical seasons, which are different than meteorological seasons, are produced by the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the winter months, the northern half of the Earth is tilted away from the sun. This position means the northern hemisphere receives the sun’s energy at a less direct angle and brings us our coolest temperatures of the year.

Since the summer solstice in June, the arc of the sun’s apparent daily passage across the sky has been dropping toward the southern horizon and daylight hours have been decreasing. Today, it will reach its southernmost position at the Tropic of Capricorn (23.5° south latitude), marking the shortest day of the year. This observable stop is where today’s event takes its name. Solstice is derived from the Latin words “sol” for sun and “sisto” for stop.

Soon, the sun will appear to move northward again and daylight hours will slowly start to increase. Marking this transition from darkness to light, the winter solstice has long been a cause for celebration across many cultures throughout human history.

Solstices and Equinoxes. Credit: NASA 

Today is the Autumnal Equinox – Here’s What That Means

Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially begins at 20:02 UTC, which is 4:02 PM Eastern Daylight Time.

The astronomical seasons, as opposed to the meteorological seasons,  are a product of Earth’s axial tilt – a 23.5° angle – and the movement of the planet around the sun. During the autumn months, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.

Since the summer solstice in June, the arc of the sun’s apparent daily passage across the sky has been moving southward and daylight hours have been decreasing. Today, the sun appears directly overhead at the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.

With the sun sitting lower in the sky and daylight hours continuing to shorten, autumn is a season of falling temperatures. According to NOAA, the average high temperature in most US cities drops about 10°F between September and October.

Earth’s solstices and equinoxes. Image Credit: NASA

Aphelion 2017: Earth Farthest from Sun Today

The Earth will reach its farthest point from the Sun today – an event known as the aphelion. It will officially take place at 20:11 UTC, which is 4:11 PM Eastern Daylight Time.

This annual event is a result of the elliptical shape of the Earth’s orbit and the slightly off-centered position of the Sun inside that path. The exact date of the Aphelion differs from year to year, but it’s usually in early July – summer in the northern hemisphere.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, Earth is about 152 million kilometers (94 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) further than during the perihelion in early January. That means the planet will move more slowly along its orbital path than at any other time of the year. As a result, summer is elongated by a few days in the northern hemisphere.

The word, aphelion, is Greek for “away from the sun”.

Earth is farthest from the Sun during summer in the northern hemisphere. Credit: TimeandDate.com

Summer Solstice 2017

Today is the June Solstice, the first day of summer in the northern hemisphere. The new season officially began at 04:24 UTC, which is 12:24 AM Eastern Daylight Time.

Our astronomical seasons are a product of the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the summer months, the northern half of the Earth is tilted toward the sun. This position allows the northern hemisphere to receive the sun’s energy at a more direct angle and produces our warmest temperatures of the year.

Since the winter solstice in December, the arc of the sun’s apparent daily passage across the sky has been moving northward and daylight hours have been increasing. Today, it reached its northernmost position at the Tropic of Cancer (23.5° north latitude) marking the “longest day” of the year. This observable stop is where today’s event takes its name. Solstice is a word derived from Latin and means “the sun stands still”.

While today brings us the greatest number of daylight hours all year (15 hours and 5 minutes in NYC), it is not the warmest day of the year.  The hottest part of summer typically lags the solstice by a few weeks. This is because the oceans and continents need time to absorb the sun’s energy and warm up – a phenomenon known as seasonal temperature lag.

Earth’s solstices and equinoxes. Image Credit: NASA

When to Expect the Final Freeze of the Season

Most people associate spring with flowers and mild weather. But as a transitional season, it can also produce a rollercoaster of temperatures, including serious cold spells. Wearing a short sleeved shirt one day and a parka the next, you may start to wonder when the cold will finally fade away.

The answer to that question largely depends on location. Below is a map from NOAA that shows the typical final freeze dates across the continental US. While actual weather conditions vary from year to year, the dates shown are based on climatology – a thirty-year average of temperature data.

Here in New York City, our last freeze of the season usually comes in mid-April.

Credit: NOAA

First Day of Spring 2017

Today is the Vernal Equinox, the first day of spring in the northern hemisphere. The new season officially began at 10:29 UTC, which is 6:29 AM Eastern Daylight Time.

Our astronomical seasons are a product of the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. Today, as spring begins, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.

Since the winter solstice in December, the arc of the sun’s apparent daily passage across the sky has been getting higher and daylight hours have been increasing. Today, the sun appears directly overhead at the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.

As a transitional season, spring is a time when the chill of winter fades away and the warmth of summer gradually returns. The most noticeable increases in average daily temperature, however, usually lag the equinox by a few weeks.

Earth’s solstices and equinoxes. Image Credit: NASA

Earth’s Perihelion 2017

The Earth will reach its Perihelion today at 14:18 UTC, which is 9:18 AM Eastern Standard Time. This is the point in the planet’s orbit where it comes closest to the Sun.

This annual event is due to the elliptical shape of the Earth’s orbit and the off-centered position of the Sun inside that path. The exact date of the Perihelion differs from year to year, but it’s usually in early January – winter in the northern hemisphere. The Earth will be furthest from the Sun in July.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, the Earth is 147.1 million kilometers (91.4 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) closer than it will be in early July. This position allows the planet to speed up by about one-kilometer/second. As a result, winter in the northern hemisphere is about five days shorter than summer.

The word, perihelion, is Greek for “near sun”.

Earth is closest to the Sun during the northern hemisphere’s winter. Credit: TimeandDate.com