CHICAGO (CBS) — It was so hot on Wednesday that WBBM Newsradio 780 couldn’t resist trying to find out if that old tale about frying an egg outside is true.

WBBM Newsradio 780’s Steve Miller hosted a very small, impromptu outdoor cooking show downtown, using a metal bench as his would-be frying surface. Some people came by to watch.

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LISTEN: Newsradio 780’s Steve Miller reports

“It looks a little runny. I don’t think it’s quite hot enough to fry an egg,” one woman said.

Of course, people try this when it gets hot every year, and have been doing so for decades. But is it even possible to fry an egg on an outdoor surface in hot weather?

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If it’s the sidewalk, the answer seems to be no. It could happen theoretically, but it doesn’t get hot enough outside to work in practice.

An egg requires a temperature of 158 degrees to become firm from its natural state of viscous liquid. To cook, the proteins in an egg must denature, then coagulate, and that process won’t start until the surface temperature in hot enough, the Library of Congress explains.

There are many variables that affect how hot a sidewalk can get, including the air temperature, the material composition of the pavement, and whether the pavement is in direct sunlight, the Library of Congress explains.

In his book What Einstein Told His Cook: Kitchen Science Explained, scientist Robert Wolke said the hottest a concrete sidewalk can get is likely 145 degrees, and its temperature will drop as soon as the contents of the egg are spilled onto it. Pavement also does not conduct heat well, so the egg will not cook evenly unless you cheat with another heat source, the Library of Congress said.

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Metal surfaces, however, are another story. People have fried eggs on the hoods of their cars in extreme heat, since metal is a far better conductor of heat, the Library of Congress said.