The weather forecast for July 4th in Philadelphia is looking good, but a first heat wave is possible
While Philadelphia initially has a chance 2022’s heatwave from Thursday assures forecasters it won’t survive a bank holiday weekend that should be at least semi-decent – and even kind to the fireworks shows and their admirers.
Temperatures are expected to rise to 90 degrees on Thursday, with a code orange alert for ozone in effect, and will climb well into the 90s on Friday, but on Saturday, Steamy air and picnic threats could limit afternoon temperatures.
And with a page about to fall off the calendar, there’s nothing in the near future for the Philadelphia area to compare to the sweltering heat that has ravaged parts of Europe, Japan and the American West this season.
» READ MORE: Forecasters see another hotter-than-normal summer for Philly
“We haven’t had sustained heat,” said Jonathan O’Brien, meteorologist at the National Weather Service’s Mount Holly office.
All of that could change before July is over, but what hasn’t happened so far this year speaks to a paradoxical trend — the lack of sustained hot spells even as summers get hotter amid accelerating warming and climate change.
It’s possible a public nemesis commonly referred to as “humidity” helped dampen the daytime heat in recent summers, said Dave Dombek, chief weather forecaster at AccuWeather Inc.
» READ MORE: Philly’s summer temperatures have risen 3 degrees since 1970 – and the nights have gotten even warmer
Whatever the reason, the trend may help explain why heat-related deaths have been declining in Philadelphia.
In the past 10 years, Philadelphia has reported a total of 44 heat-related deaths. According to the health department, almost 400 cases were registered in the 10 years up to 2002.
NOAA, the CDC and public health experts have praised Philadelphia’s aggressive heat wave response system, which was implemented in 1995, two summers after the deadliest summer on record with 118 heat-related deaths.
If the National Weather Service and the Department of Health declare a heat emergency — which is unlikely to happen this week — refrigeration centers will open and the Philadelphia Corporation for Aging will extend its “hotline” hours. In addition, block captains are being called upon to care for elderly people living alone, of whom the city has about 150,000 according to census figures.
Philadelphia pioneered the method of counting heat-related mortality by including cases where heat was a contributing cause – as opposed to only counting confirmed cases of hyperthermia, a core body temperature of 105 Fahrenheit.
» READ MORE: For a day, Philly residents take to the muggy streets to measure heat and pollution
Since it would be impossible to reach all victims in time to confirm hyperthermia, then the city is there–The coroner ordered staff to look for forensic clues, such as fans running in a room with the windows closed.
NOAA and the CDC recommended other cities to adopt Philadelphia’s strategies, and health experts credited the city with raising awareness of potentially deadly heat hazards and saving lives.
But lately, at least, the data suggests that Philly has received help from the atmosphere in reducing heat mortality numbers.
In the summers of 1993, 1995, and 1999, the city recorded a total of 266 heat-related deaths. All three years were marked by long, grueling heat waves. The longest, in 1995, lasted 17 days.
In the past 10 years, 2012 saw 10 consecutive days with temperatures of 90 degrees or more.
» READ MORE: Summers are hotter but heat-related deaths have fallen. Philadelphia has a lot to do with it.
Conversely, the past 10 years have produced a crop of heat waves that have lasted only three to five days, with more than three on average and five last year. On average over the previous six decades, these had occurred less than twice per summer.
That may have something to do with more moisture in the air and on the ground, Dombek said. Rain has a way of making rain.
Summers have generally been wet here — like June with over 5 inches of rain in Philly — and the region has not had a serious drought in 20 years. This could well be related to the global warming trend; warmer air can hold more water vapor.
“It seems like every time you get a short-term drought, it gets hit back, and sometimes a big time,” Dombek said.
“When the ground is wetter than normal, it doesn’t get as hot,” he said. The more energy the sun spends evaporating puddles and splashing water droplets off leaves, the less energy it has left to heat the surface.
The sun will likely have more water to evaporate on Saturday, but chances are most of Sunday and perhaps all of Monday will be dry, the weather service’s O’Brien said, with temperatures hovering in the 80s on both days. years lay.
“Monday looks like the choice of bank holiday weekend at this point,” he said, and as for the bomb blasts, the fireworks prospect “looks good.”