What is Indian Summer?

Autumn is a season known for changing leaves and falling temperatures. Every once in a while, however, summer warmth makes a resurgence. When this happens, it is often dubbed an “Indian Summer”.

This weather phenomenon, according to the NWS glossary, is defined as “an unseasonably warm period near the middle of autumn, usually following a substantial period of cool weather.”  In the northeastern US, it is generally associated with an area of high pressure to the south that ushers warm air northward.

In popular use since the 18th century, the exact origins of the term “Indian Summer” are a bit foggy. One of the more reasonable explanations behind this unique phrase suggests a connection to when Native Americans began their hunting season, but no one knows for sure.

In other parts of the world, this summer-like weather goes by a variety of different names. In Europe, a number of countries associate the unusual warmth with the nearest saint’s day. It is known as “St. Luke’s Little Summer” if it develops in October or a “St. Martin’s Summer” if it occurs in November. In temperate parts of South America, it is simply known as “Veranico” (little summer).

Regardless of its name, the timing and intensity of these autumn warm spells vary from year to year. Nevertheless, when they do occur, they usually only last a few days. So, as we inevitably move toward winter, enjoy them while they last.

Autumnal Equinox 2016

Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially begins at 14:21 UTC, which is 10:21 AM Eastern Daylight Time.

The 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 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 our sky has been moving southward and daylight hours have been decreasing. Today, it crossed 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

Earth’s solstices and equinoxes. Image Credit: NASA

NYC Monthly Summary: October 2015

October was a weather roller-coaster in New York City this year. We had highs that ranged from a relatively balmy 78°F to a chilly 50°F.  In the end though, the warmth won out. The city’s mean temperature for the month was 58°F, which is 1.1°F above average.

On the precipitation side of things, October was mostly dry and marked the city’s fourth consecutive month with below average rainfall. In all, we received 3.91 inches of rain in Central Park, which is 0.49 inches below normal. Of this total, 1.44 inches fell in a single heavy rain event during the last week of the month. Despite this soaker, the city remains in a moderate drought according to the latest report (released on 10/29) from the US Drought Monitor.

October was a temperature roller-coaster in NYC. Credit: The Weather Gamut

October was a temperature roller-coaster in NYC.  Credit: The Weather Gamut

Autumnal Equinox 2015

Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially began at 8:21 UTC, which is 4:21 AM Eastern Daylight Time.

The 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 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 our sky has been moving southward and daylight hours have been decreasing. Today, it crossed 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.

Solstices and Equinoxes. Credit: NASA

Earth’s solstices and equinoxes. Image Credit: NASA

Equinox

The Earth’s axis is tilted neither toward nor away from the sun on the Equinox. Image Credit: NASA

NYC Monthly Summary: October 2014

October was a bit of weather roller coaster in New York City this year. We had highs ranging from a chilly 53°F to a balmy 77°F. In the end though, with 19 out of 31 days posting warmer than average readings, the warmth won out. All together, the city’s mean temperature for the month was 59.6°F. That is 2.6°F above average.

In terms of precipitation, the city was fairly soggy this October. Central Park measured 5.77 inches of rain, which is 1.37 inches above normal. Most of this came down during three significant rain events that each produced more than an inch of rain in a 24-hour period.  Nonetheless, following a parched August and September, NYC and its surrounding area is still listed as “abnormally dry” on the latest report from US Drought Monitor.

Oct2014_temp

Credit: The Weather Gamut

Oct2014_Rain

Credit: The Weather Gamut

Autumn Considered the Second Season for Tornadoes

Spring is the season most commonly associated with twisters in the United States. Autumn, however, can be just as dangerous and is known as the “second season” for tornadoes.

According to NOAA, approximately 1200 tornadoes touch down in the US every year. While most occur in “Tornado Alley”, in the central part of the country, activity there tends to peak in May. The second season is most active in the mid-south, an area often referred to as “Dixie Alley”.

During the transitional months of autumn, the jet stream frequently dips south bringing cooler air into the region. At the same time, warm, moist air is flowing in from the Gulf of Mexico. When these two different air masses meet, the local weather can get very active. In fact, some of the largest tornado outbreaks of any month have occurred in October and November.

Credit: USTornadoes

Credit: USTornadoes.com

Credit: USTornadoes

Credit: USTornadoes.com

Autumnal Equinox 2014

Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially begins at 02:29 UTC, which is 10:29 pm Eastern Daylight Time.

The 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 fall 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 summer solstice in June, the arc of the sun’s daily passage across our sky has been moving southward and daylight hours have been decreasing. Today, it crossed 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, autumn is a time when the heat of summer fades away and the chill of winter gradually returns. The largest drop in average temperature, however, usually lags the equinox by a few weeks.

Seasons

Earth’s solstices and equinoxes. Image Credit: NASA

Equinox

The Earth’s axis is tilted neither toward nor away from the sun on the Equinox.                   Image Credit: NASA

NYC Monthly Summary: September 2013

September 2013 was a bit of a weather roller coaster in New York City.  We had high temperatures that ranged from a sweltering 96°F to a cool 65°F.  All together, though, the city’s average monthly temperature was 68°F, which is exactly normal.  Transitioning from summer to autumn, these wide fluctuations are not that unusual.

In terms of precipitation, the city was mostly dry.  We received 2.95 inches of rain in Central Park, most of which fell during two separate heavy downpours. Nonetheless, we were still 1.33 inches below normal.  September now marks the third consecutive month that the city received below average rainfall.

Sept_tempsGraph Credit: The Weather Gamut

Autumnal Equinox 2013

Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially arrives at 20:44 UTC (4:44 PM EDT) when the sun is directly in line with the Earth’s equator.

Seasons are the result of the tilt of the Earth’s axis, a 23.5° angle. Today, as autumn begins, the planet’s axis is tilted neither toward nor away from the sun. As a result, we receive approximately equal hours of day and night. Derived from Latin, the word “equinox” literally means “equal night”.

As a transitional season, autumn is a time when the heat of summer fades away and the chill of winter gradually returns. The largest drop in average temperature, however, usually lags the equinox by a few weeks.

Autumnal Equinox.  Image Credit: Image Credit: Przemyslaw “Blueshade” Idzkiewicz

The angle of the sun’s rays hitting the Earth on the Autumnal Equinox.

Image Credit: Przemyslaw “Blueshade” Idzkiewicz

First Taste of Fall in NYC

Autumn’s chill arrived in New York City this weekend, two weeks after the official start of the season.

Following days of above average warmth, temperatures dropped dramatically overnight on Saturday when a cold front moved through the region. This arctic blast brought the city its coldest air of the season to date.  Daytime highs plummeted from 78°F on Friday to 54°F on Sunday.

This jarring cold snap is a reminder that what goes up must come down, especially in a transitional season like autumn.  Forecasters expect to see a rebound in temperatures later this week, but only to seasonal levels.

Graph Credit: The Weather Gamut