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It’s not record-breaking heat. The temperature has hit 100 degrees only once so far this year – and that was yesterday, briefly, in Newark. Still, for the last week, going from air conditioning to the outdoors has felt like walking into a concrete wall of heat. And it’s been, at best, uncomfortable for the entire month.
But the real problem hasn’t been the heat — it’s been the humidity.
“Yes, it has been high, and yes, as a result of all of the rain we’ve had,” said David Robinson, New Jersey State Climatologist. “This has resulted in nighttime minimums being quite elevated, often above 70 and consistently in the upper 60s or higher since June 23. While not a record run, it is impressive.”
Although July precipitation so far is running about average, June’s 9.57 inches of rain was the wettest on record – dating back to 1895. Humidity levels have been peaking above 90 percent on average across the state, and 10 locations — from the High Point Monument down to Hamilton, Atlantic County — have consistently been stuck with 100 percent humidity on most days this month.
Robinson said the temperatures are not as warm as they might be because of all the rain in the surface” in June, as “some of the sun’s heat has gone to evaporating moisture, not heating the air down here.”
But combining the peak heat and humidity readings this week using the [link:http://www.nws.noaa.gov/os/heat/index.shtml#heatindex|
National Weather Service’s heat index calculator], which measures how it really feels outside, the numbers were literally off the charts.
On Wednesday, when the mercury in Woodstown hit 95 degrees with 100 percent humidity, the heat index measured 161 degrees Fahrenheit. The NWS Heat Index chart only goes as high as 137 degrees, but the Weather Service cautions that, in full sun, index values increase by up to 15 degrees.
According to that chart, it has been dangerous or extremely dangerous to do either prolonged or strenuous activity outdoors all week in much of New Jersey.
Robinson said this month “is already just about a lock for one of the top 10” warmest Julys in the state’s recorded history. While the hottest July was in1955, with an average temperature of 79 degrees, seven of the other nine warmest Julys have occurred since 1993, with 2011 coming in a close second at 78.8 degrees.
“We’ve had several days in the past three summers where a fair number of stations have reached the century mark,” Robinson said. “This heat wave, and the summer to date, has not provided such … Still, it has been warm. Hot Julys have become rather commonplace of late!”
While no single day’s weather, a single heat wave or even a single hot summer can be attributed to global warming, Robinson said the trend is clear.
“New Jersey is getting warmer, be it in July, other months or annually,” he said. “2012 was the warmest calendar year on record in New Jersey. 2013 isn’t quite as warm, but is running on the warm side. One should never expect each successive year to be warmer than the last…..even in this warming world. However there is no denying that New Jersey, the U.S. and the globe are warming in recent decades. And yes, this is in large part due to human impacts on the environment.”