The expression, “it’s so hot you can fry an egg on the sidewalk” seems intended as hyperbole, but some people take it as a challenge — or maybe they’re just trying to expand their culinary skills.
Concrete or Asphalt?
The notion of frying an egg on the sidewalk is so popular that there’s a National Fry an Egg on the Sidewalk Day on July 4. It’s usually hot, and people are already out doing peculiar things, such as setting off fireworks and competing to see who can eat the most hot dogs.
Every July 4, the town of Oatman, Arizona, sponsors a solar egg frying contest, though Oatman’s rules are relaxed — they don’t require sidewalks, and they allow mirrors and magnifying glasses.
The problem for would-be sidewalk chefs isn’t so much the temperature, but the cooking surface. Sidewalks are typically made of concrete, and concrete is a poor conductor of heat. Even if the sidewalk is hot enough, it’s not likely to transfer enough of that heat to the egg to get it ready for your toast.
If you’re determined to give this a try, asphalt is a better bet. Reporters in Phoenix, Ariz. measured the temperature of the asphalt on the city’s streets during the 2018 heat wave and got readings of a sizzling 161 degrees Fahrenheit.
This is especially important information for dog owners trying to protect their puppies’ paws, which is usually why municipalities take the temperatures of their streets. It’s also useful for would-be outdoor egg cooks.
According to the American Egg board, egg whites coagulate between 144 and 149 degrees Fahrenheit. Yolks need a bit more heat, firming up at temperatures between 149 and 158 degrees.
In Phoenix, the street would seem plenty hot, but it still might not be what you need to make a decent breakfast.
Other Hot Surfaces
Robert Wolke explains in his book, What Einstein Told His Cook: Kitchen Science Explained, there is another challenge of street egg-cookery. When the egg hits the street, the surface cools slightly, making the egg nowhere near 161 degrees. Because there’s no burner beneath the street to quickly crank up the heat, the surface temperature won’t recover quickly like it would in a pan on your stove.
Even if the surface heat of the street is intense, you’re probably going to need a skillet to conduct that heat. Some have had luck frying an egg in the street on a 115-degree Arizona day using a cast-iron skillet — preheating the skillet in a car can help.
Others recommend using metal pans and doing the cooking on the hood of a car, rather than the street. And if you decide to hatch this plan, be sure to use a pan of some kind. You don’t want to deal with the results of breaking an egg on your car, whether the egg fries.
But once we’ve moved to the street, or the hood of a car, and added refinements like skillets, we’ve strayed from the initial challenge: frying an egg on the sidewalk. That’s probably not doable unless the street temperature gets a lot higher. Of course, with the way things are going, that could happen. They may soon tighten the contest rules and still have a winner in Oatman.
Meanwhile if, like most sensible people, you think that when the street temperature reaches 160 degrees, it’s better to just stay inside, you might want to try your hand at cooking salmon in the dishwasher.