In a city where summer is being marked with multiple heat waves — this week’s forecast is calling for extreme heat — questions can arise over the specifics of those temperatures.

Such as: Why, in some areas, does it feel hotter than the National Weather Service says it is? Where is the temperature projected on our weather apps actually measured?

One reader who submitted an inquiry through Curious Philly, the portal where our journalists answer your questions, wanted to know just where the weather service takes its measurements, and how that temperature might differ from other places'.

Temperature generally is measured around the country at airports, so when you open your weather app on your phone, the temperature you see was measured at the closest airport to you.

If you are near Philly, this is Philadelphia International Airport, where the official measurements for temperature, precipitation, wind, and other weather conditions are taken.

A spokesperson at the National Weather Service office in Mount Holly said temperature is commonly measured at airports because it is easier than doing it in the middle of the city.

According to the weather service, airports are chosen to record temperatures for a variety of reasons, primarily because they are open spaces with grass and free from factors like gas emissions and buildings.

In New York City, however, temperature is measured at Central Park.

While it’s unlikely that temperatures in Center City differ greatly from what’s recorded at the airport, according to the weather service, the temperature does fluctuate based on location.

According to a neighborhood map The Inquirer compiled last summer using data supplied by David Hondula at Arizona State University, Center City is likely to be one to two degrees warmer than Philadelphia’s temperature average.

Certain spots — areas in North Philadelphia, South Philadelphia, and West Philadelphia, all with lots of rowhouses — are far warmer than the city average due to “heat-trapping pockets of the city made extra steamy by block after block of black-roofed rowhouses, strip shopping centers, busy roads — but few trees or other sources of shade in between,” The Inquirer reported.

The Hottest Places in Philadelphia on a Summer Day

Some areas of Philadelphia can be more than 5 degrees warmer than the city average on a hot summer day, due to heat trapped by rowhouses, streets, and other hard surfaces. By contrast, parts of the city that have parks and an abundance of shade trees can be more than 10 degrees cooler than the city average. The map below reflects surface temperatures.

Click and zoom in on the map for more information.
SOURCE: David Hondula, Arizona State University
JOHN DUCHNESKIE / Staff Artist

Some of these places, like Hunting Park in North Philly, can get more than 5 degrees hotter than the average for the city.

Other areas are notably cooler — particularly places that have an abundance of trees and shady parks, like Chestnut Hill and Mount Airy in Northwest Philly, and Somerton in the Northeast. So it may be worth a trek to these shady areas this weekend.