Tag Archives: summer

Heat Index

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Temperature is one of the basic elements of weather.  Our perception of it, however, is often influenced by other factors.  In summer, this is usually humidity.

The heat index, developed in the late 1970’s, is a measure of the apparent or “real feel” temperature when heat and humidity are combined.  Since the human body relies on the evaporation of its perspiration to cool itself, the moisture content of the air affects comfort levels. Basically, as humidity levels increase, the rate of evaporation decreases and the body can begin to feel overheated.  For example, an air temperature of 92°F combined with a relative humidity level of 60% will produce a heat index value of 105°F.

The National Weather Service issues heat advisories when the heat index is forecast to be at least 95°F for two consecutive days or 100°F for any length of time.  Extended exposure to high heat index values can lead to serious health hazards.

Heat-IndexImage Credit: NOAA

Summer Solstice 2013

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Today is the June Solstice, the first day of summer in the northern hemisphere. The new season officially began at 5:04 UTC, which is 1:04 Eastern Daylight Time.

Astronomical seasons are the result of the tilt of the Earth’s axis, a 23.5° angle. Today, as summer begins, the northern half of our planet is slanted toward the sun.  This position allows the northern hemisphere to receive the sun’s energy at a more direct angle, warming the entire region.

The summer solstice is often called the “longest day of the year”.  This, however, is a bit of a misnomer as one day always contains twenty-four hours.  Nonetheless, today is the day with the longest duration of daylight. Since the winter solstice in December, the sun – in its apparent seasonal journey across the sky – has been making its way north. Reaching its northern-most position at the Tropic of Cancer today, it stopped.  This phenomenon is where today’s event takes its name. Solstice is a word derived from Latin meaning, “sun stands still”.

SeasonsImage Credit: NASA

A Late Spring Heat Wave in NYC

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Temperatures have been soaring in the northeastern United States.  In fact, it feels like mid-summer and the start of that season is still more than two weeks away.

In New York City, temperatures reached 90°F for three consecutive days.  This marks the city’s first official heat wave of the season.  Our normal high for this time of year is a more moderate 75°F. This extreme heat also caused a number health concerns, including air quality alerts.

The dramatic rise in temperature across the region was the result of a Bermuda High – an area of high pressure that steers hot air from the Gulf of Mexico toward the northeast.  The summer-like conditions of this weather pattern, however, are expected to come to a stormy end late tonight as a cold front moves into the area.

A Brief Taste of Summer in NYC

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The Big Apple had a sweet, but brief, taste of summer this week.

The city’s high temperature reached 82°F on Tuesday, which is 23°F above average.The warm conditions did not last long, however.  In fact, they ended with a bang as a severe thunderstorm rolled through the area mid-week.  Producing strong winds and heavy rain, the storm ushered in cooler air and brought temperatures back to more seasonable levels.

Despite the rollercoaster-like sensation that dramatic temperature swings produce, this recent warm-up was a welcome change of pace for many winter-weary New Yorkers.

AprilTempSwingGraph Credit: The Weather Gamut

Third Hottest Summer for U.S.

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Summer is a season known for high temperatures.  This year, however, they were more extreme than usual across much of the United States.

According to the National Climatic Data Center report released this week, Summer 2012 was the third warmest summer ever recorded in the lower forty-eight states. As a whole, the nation averaged a temperature of 74.4°F, which is 2.3°F above the long-term norm. Only the summers of 1936 (74.6°F) and 2011 (74.5°F) were hotter.

This summer’s exceptional heat follows both a record warm spring and winter.  In fact, 2012 – to date – has been this country’s warmest year on record.

NYC Monthly Summary: August 2012

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August was another warm month for New York City. We had three days when the mercury reached 90°F or above. This helped drive the city’s average monthly temperature up to 76.7°F, which is 1.69°F above normal.

On the precipitation front, a number of thunderstorms rolled through NYC this August. Although they brought periods of heavy rain, the city finished the month on the dry side.  We collected a meager 2.91 inches of rain in Central Park, which is 1.53 inches below normal.  This is a huge departure from the record rainfall – 18.95 inches – which we received in August last year.

Graph Credit: The Weather Gamut

The Hottest Month Ever in the U.S.

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High temperatures are not uncommon for July in the U.S., but this year they were extreme.  July 2012 now marks the hottest month ever recorded in the lower forty-eight states.

According to NOAA’s monthly climate report, the country averaged 77.6°F this July.  That is 3.3°F above the 20th century average and breaks the previous record set during the Dust Bowl in July 1936.

Most of the heat last month was centered in the mid-west and central plains, where it fueled the region’s devastating drought. By the end of the month, more than 60% of the U.S. was in a state of moderate drought or worse.  These hot and dry conditions were ideal for wildfires, which scorched more than two million acres nationwide in July alone.

On the whole, this year has been exceptionally warm across the contiguous United States.  In fact, the period of January through July 2012 now stands as the warmest seven months this country has seen since modern record keeping began in 1895.

NYC Monthly Summary: July 2012

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July is generally the warmest month on the calendar for New York City, and this year temperatures soared. We had ten days when the thermometer read 90°F or above, including July 18th when the mercury hit 100°F in Central Park.  This extreme heat helped raise the city’s average monthly temperature to 78.8°F, which is 2.3°F above normal.

In terms of precipitation this July, NYC experienced a number of severe thunderstorms, which brought much-needed rainfall to the area. In the end, however, the city only collected 4.21 inches of rain, which is 0.39 inches below normal. While not in a drought, it is interesting to note that the city has received below average precipitation for six out of the past seven months.

Graph Credit: The Weather Gamut

A Summer Sea Breeze

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While spending a weekend at the beach recently, I was reminded how pleasant a sea breeze can feel on a hot summer afternoon.

A sea breeze is a localized, daytime wind driven by the temperature difference between land and a large body of water. Since land is able to absorb the sun’s energy more quickly than water, it warms faster. As a result, air over the ground heats and rises, creating an area of low pressure. Cooler air is then drawn from the zone of higher-pressure above the ocean to fill the void, forming an onshore breeze.

These winds typically start flowing around mid-day and last throughout the afternoon.  They are valued for their moderating influence on local temperatures, keeping coastal areas cooler than their inland neighbors during the warmest months of the year.

Image Credit: physicalgeography.net

Widespread U.S. Drought

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Drought, an extended period of below average precipitation, has been plaguing many parts of the United States this summer.

According to the U.S. Drought Monitor, 61% of this country is currently suffering in a state of moderate drought or worse. This is the largest area ever recorded in the monitor’s twelve-year history.

Experts say that this year’s widespread drought has been developing for months and cite the unusual position of the jet stream as a key factor.   Often referred to as the “storm track”, the jet stream typically travels across the middle of the country in winter and spring, bringing vital snow and rain to the region. This year, however, it has been persistently flowing far to the north.  As a result, abnormally hot and dry conditions have been dominating much of the nation.

Without any soaking rains in the forecast, this drought is expected to get worse before it gets better.

Image Credit: US Drought Monitor