Tag Archives: summer

The Dew Point Makes a Difference

Posted on by

“It’s not the heat, it’s the humidity.” This common refrain heard throughout much of the eastern U.S. in summer refers to how the amount of water vapor in the air affects human comfort. Since the main source of body cooling is evaporation of perspiration, the higher the moisture content of the air, the less evaporation takes place and the warmer we feel. One measure of atmospheric moisture is the dew point temperature.

The dew point, as defined by the NWS, is the temperature to which air must be cooled in order to reach saturation. In other words, the difference between the air temperature and the dew point temperature tells you how much moisture is in the air. The greater the distance between the two, the dryer the air is. Conversely, the closer they are together, the higher the moisture content of the air.

While everyone has a different tolerance for humidity, in summer – when air temperatures tend to be high – a dew point temperature of 50°F is generally considered comfortable. Dew points in the 60s are thought of as muggy and once they reach the 70s or higher, the air can feel down right oppressive. On the opposite end of the spectrum, dew points in the 40s or lower are considered dry. Dry air has its own set of comfort issues, including skin irritations.

September Brings NYC Warmest Day of the Year

Posted on by

The summer months of June, July, and August have come and gone, but Tuesday brought New York City its hottest day of the year (so far). The high temperature in Central Park soared to 92°F.

According to the NWS, it was our warmest day since September 11, 2013 when the high was 96°F. The normal high in NYC at this time of year is 80°F.

Highlighting the relatively mild conditions that dominated this summer, Tuesday was also only the seventh time this season that the temperature reached 90°F or higher. The city, on average, typically sees fifteen 90-degree days per year.

Credit: The Weather Gamut

Credit: The Weather Gamut

NYC Monthly Summary: August 2014

Posted on by

Continuing this summer’s trend, August 2014 hovered around average in New York City. While sixteen out of thirty-one days posted below average temperatures, three days reached the 90°F mark.  All together, the city’s mean temperature for the month was 74.4°F. That is only 0.6°F below normal.

In terms of precipitation, the Big Apple was mostly dry this August. Despite a few thunderstorms and heavy downpours, the city only received 2.25 inches of rain in Central Park. That is 2.19 inches below normal.

Credit: The Weather Gamut

Credit: The Weather Gamut

Credit: The Weather Gamut

Credit: The Weather Gamut

A Late Summer Warm Up in NYC

Posted on by

It’s the last week of August and it finally feels like summer in New York City. The high temperature in Central Park has been in the upper 80’s for the past few days and today it soared to 90°F. This is worth noting, because high heat has been something of a rarity in the Big Apple this summer.

This season to date, NYC has only had five days reach 90°F or higher. On average, we typically get fifteen. Looking back, every month this summer brought a noticeable dearth of extreme heat. June had zero days with temperatures at or above 90°F, July had three and August (so far) has only had two.

The most 90-degree days that the city has ever had in one year, according to NWS records, was thirty-nine. That happened in both 1991 and 1993. On the opposite end of the spectrum, 1902 only had one day hit the 90°F mark.  Last summer, we made it to 90°F or higher seventeen times.

Swamp Coolers

Posted on by

Coming from the humid east coast, one of the first things you notice upon arrival in the southwestern United States is how dry the air is. Dew points are often in the 40s while the air temperature soars into the 80s and 90s during the summer. This is why swamp coolers are popular in the region.

A swamp cooler is an evaporative cooling device. It takes hot, dry outside air and blows it across water soaked pads. This allows the process of evaporation – the transition of liquid water to water vapor – to cool the air that is pumped into a building. It also adds some moisture to the inside air, making it more comfortable.

While the U.S. Energy Department says swamp coolers cost about one-half as much to install as central air conditioners and use about one-quarter as much energy, they do not work well everywhere. In hot, muggy climates, for example, the high relative humidity would significantly reduce the rate of evaporation. Moreover, adding extra water vapor to the air would not be considered a bonus in an already uncomfortably humid environment.

For this reason, only 3% of homes nationwide utilize swamp coolers, according to a report from the Energy Information Administration. In the arid Rocky Mountain region, however, they are found in more than 26% of all households.

Sign advertising swamp coolers in Salida, CO. Image Credit: The Weather Gamut

Sign advertising swamp coolers in Salida, CO.   Image Credit: The Weather Gamut.

NYC Monthly Summary: July 2014

Posted on by

July 2014 was fairly mild in New York City with a noticeable lack of extreme heat. On average, July typically brings the Big Apple six days with readings of 90°F or higher. This year, however, there were only three. That includes the first 90° day of the season. In the end, the city’s mean temperature for the month was 76.1°F. That is only 0.1°F above normal.

In terms of precipitation, July is usually NYC’s wettest month and this year it lived up to expectations. In fact, it was the city’s wettest July in five years. We received 5.59 inches of rain in Central Park, which is 0.99 inches above average. Most of this total came down in three significant events associated with heavy thunderstorms.

Credit: The Weather Gamut

Credit: The Weather Gamut

Credit: The Weather Gamut

Credit: The Weather Gamut

Heat Lightning

Posted on by

When lightning flashes in the sky without a clap of thunder, it is called “heat lightning.” This, however, is a bit of a misnomer as it is not a special form of lightning and it is not generated by heat. In fact, it is just normal lightning that is too far away for the sound of thunder to be heard.

Lightning travels near the speed of light – 186,000 miles per second. Even at a distance of 10 miles, you will see it almost instantly. Thunder, on the other hand, travels at the speed of sound – about one mile in five seconds near the ground. It is often refracted through the atmosphere and reflected by the Earth’s surface, dissipating the sound. For this reason, thunder is rarely heard at a distance of more than 10 miles from where the lightning actually occurred.

The origins of the term, “heat lightning”, are probably linked to the fact that it is most often seen on hot, humid summer nights.

Weather History: NYC’s Hottest Day

Posted on by

On this date in 1936, the temperature in New York City soared to 106°F. It was the hottest day ever recorded in the Big Apple.

This triple digit heat was part of an extreme heat wave that impacted most of the mid-west and northeastern United States. It was an extension of the massive heat dome that built up over the Great Plains a few weeks earlier. Nationwide, this extreme heat caused approximately 5000 deaths, nearly 100 of which were in NYC.

During the 1930’s – the height of the Great Depression – air conditioning was not very common. Many New Yorkers sought relief at city beaches and parks. At night, some even slept outdoors.

More recently, it is interesting to note that between 2000 and 2009, NYC only had one 100°F day. In the last four years, however, we have had five days hit the century mark.

New Yorkers crowd the beach at Coney Island during the heat wave of 1936. Image Credit: NY Daily News

New Yorkers crowd the beach at Coney Island during the heat wave of 1936.                              Image Credit: NY Daily News

Earth’s Aphelion 2014

Posted on by

The Earth will reach its aphelion today at 8 P.M. Eastern Daylight Time.  This is the point in the planet’s elliptical orbit where it is farthest from the Sun.

Today, the Earth is about 152 million kilometers away from its nearest star.  That is approximately 5 million kilometers further than during the perihelion in early January. The exact date of the aphelion differs from year to year, but it’s usually in early July.

While the planet’s distance from the Sun does not cause the seasons, it does influence their length.  As a function of gravity, the closer the planet is to the Sun, the faster it moves. So, at the aphelion, the Earth 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 sun”.

Image Credit: mydarksky.org

Image Credit: mydarksky.org

NYC’s First 90-Degree Day of the Year

Posted on by

Summer officially began last month, but the season’s heat is just now getting into full swing in New York City.

In Central Park today, the temperature soared to 91°F. That marks the city’s first 90° day of the year.   While readings in the 90s are not unusual for the Big Apple in July, they typically premiere earlier in the season. In fact, with records dating back to 1869 for Central Park, the NWS reports that only nineteen years have failed to produce a 90°F day before the end of June.

On average, according to the NWS, the city generally sees its first 90°F day by June 3rd. Its earliest was April 7, 2010 and its latest was July 26,1877. Last year, NYC’s first 90°F reading was on May 30th.