It’s not 100 degrees until DFW Airport says it is

The temperature reached 100 Sunday afternoon at Meacham Airport in Fort Worth. The same reading was recorded at Naval Air Station Fort Worth.

The next day, it reached 101 at Meacham and 100 at the air station and Arlington Municipal Airport. And it was at least 100 on Tuesday, Wednesday and Thursday at Meacham.

None of those readings are considered official for North Texas, however, because they were not recorded at the National Weather Service’s official observation site.

So while it’s been really hot the past couple of weeks, it hasn’t officially hit 100 this summer. And it won’t until that temperature has been registered at the thermometer near Runway 17C at Dallas/Fort Worth Airport.

Situated within a collection of weather gauges that measure everything from precipitation to ceiling height, the official thermometer of North Texas has been in the same spot for 20 years.

“Once an official observation site has been established, you don’t want to move it unless there’s a compelling reason,” said Tom Bradshaw, the meteorologist in charge at the National Weather Service in Fort Worth.

Since weather data started being recorded in 1898, the measuring sticks have moved around.

The first official site was at an old federal building, near what is now Fort Worth City Hall. It then moved to the fifth floor of the present-day U.S. Courthouse.

In the 1950s, it moved to Amon Carter Field (later known as Greater Southwest Airport) in east Fort Worth before moving to DFW when it opened in 1974. At DFW, the measurements were first taken near a Delta Air Lines hangar before the site moved to its current location in 1995.

From Dallas County?

Bradshaw said there were valid reasons to move the official weather station.

“In the case of moving Fort Worth’s official site from downtown to the airport locations through the years, it’s simply due to the fact that commercial aviation safety dictated that accurate weather observations be taken at the airports,” he said.

Not all official weather sites are at airports. Bradshaw noted that one of New York City’s is in Central Park.

While the official measurements for the DFW area were taken in Fort Worth through 1974, that’s no longer true. Both the current and the former DFW Airport weather stations are in Dallas County, airport spokesman David Magaña said.

Meacham is a hot spot

Subtle differences in readings are often due to where the temperature is taken. For years, Dallas Love Field tended to be hotter than everywhere else during summer.

But when the instruments were moved from a rooftop to the ground, that changed, said Skip Ely, who retired as the Fort Worth office’s meteorologist in charge in 2001.

Now, he said, Meacham is the hot spot.

“I find Meacham to be just slightly warm,” Ely said. “That’s probably just siting issues. At DFW, it’s in a grassy area fairly far from the runway. It compares favorably with my porch thermometer in North Richland Hills.”

Some may quibble that DFW hasn’t reached 100 when other places have, but Ely said he believes the airport readings are accurate.

“My casual observation when I was working was that DFW was a pretty good site for our weather records, probably the best for all of our weather observations,” Ely said. “The one at McKinney would tend to read lower while Denton and Alliance seem to have very similar readings. My conclusion was DFW was a pretty good site.”

This story was originally published July 23, 2015 at 6:17 PM with the headline "It’s not 100 degrees until DFW Airport says it is."