Yesterday, an image went viral on social media which showed a high frequency of contrails in the Houston skies. Generally, you may see the odd contrail if you look up, but this was clearly much more extreme and unusual compared to the norm.

The contrails were originally photographed and uploaded to Reddit by a curious user who asked about them. Although this may be the source of intrigue, it turns out that there’s a perfectly reasonable explanation, and it’s actually quite mundane.

As one user explained, contrails can often stay visible for long periods of time, depending on the weather conditions. Here, they can persist for a few minutes or for hours, depending on the humidity and temperature of the air. They can eventually dissipate or spread out and merge with other clouds. In some cases, contrails can even form into cirrus clouds, which are wispy, high-altitude clouds that are made up of ice crystals.

Contrails are composed of water vapor that condenses into ice crystals when it cools to below freezing temperatures in the high altitudes where aircraft fly. Contrails typically form when the air is very dry and the aircraft is flying at a high altitude. They are most commonly seen during the day when the sun shines on them, causing them to reflect sunlight and appear as white lines in the sky. In short, Houston had ideal conditions for this sight to take place yesterday, which is exactly what happened.