Did Interstate Roads In Houston Create Clouds?

Still image of clouds forming over Houston, Texas.

NOAA via Dakota Smith

A compelling satellite loop from Tuesday morning was shared on the social media platform X by meteorologist Ethan Mok. It showed clouds in perfect alignment with the interstate roads around Houston. Before you dismiss this as AI-generated foolishness, let me introduce you to scientific evidence that has consistently established that cities can create their own clouds and rainfall.

The Urban Cloud Effect

For 30 years, I have done research on how urban landscapes affect clouds, rainfall and storms. In fact, we have published a series of observational and modeling studies on how cities like Houston affect clouds, rainfall, and storms. However, the satellite imagery below is compelling validation of our work over the years. Dakota Smith, one of the nation’s top satellite meteorologists, was also stunned. “This is something I have never seen before on satellite…. Clouds perfectly outlining roads. Just incredibly neat imagery of Houston, Texas this morning,” he wrote in a public post on Facebook. Watch below as cumulus clouds over Houston seem to perfectly align with the interstate roadways of Houston. So what's going on?

How Did This Happen?

William Burgett-Merkel is from the Houston area and is one of my graduate students at the University of Georgia. He wrote to me early Wednesday morning asking if I had seen it and inquiring about what might be happening. Of course, I had seen it. Jordan McLeod, who recently served as a meteorology instructor at the University of South Alabama, had also shared it with me the previous evening. McLeod is an incoming doctoral student at UGA and has collaborated with me for years on this very topic. Our 2024 study actually identified a possible “urban cloud effect” for the city of Augusta, Georgia. A 2023 study of 447 U.S. cities used NASA MODIS cloud data and found that the urban environment affects the evolution and initiation of clouds. A 2019 study found similar results over Europe. However, the “urban cloud effect” is still not as well-studied “urban rainfall effect," which has now been conclusively established by many studies.

Our 2025 study, funded by a NASA Interdisciplinary Studies program, focused on the role urban surfaces and aerosols play in rainfall formation over the Houston area. We found that warmer urban land surfaces alter cloud formation, rainfall, and lightning. Because of the color and physical properties of pavement, it heats up quickly and creates a surface urban heat island. The flux of sensible heat from the warmer paved surface could have given the atmosphere enough of a boost to cause clouds. But why haven’t we seen such compelling imagery before given that high-resolution satellite data has been around for years?

Tom Mote is a climate expert at the University of Georgia and has also examined the effect of cities on rainfall. Mote also found the Houston imagery to be quite compelling. However, he wondered if a very specific set of conditions related to vertical atmospheric structure and moisture were required for this to happen. He mentioned that very specific conditions are required for an aircraft to produce a contrail. What “perfect” conditions were present to reveal these road-induced “cloud streets” on this particular day?

Burgett-Merkel asked me if aerosols associated with the early morning commute could be a factor. My gut instinct is no. We certainly know that aerosols like dust, soot, clay and other particulates in the air are important for cloud formation. Every cloud droplet requires a “seed” or condensation nucleus in its microphysics journey. We also know that there are discernible aerosol cycles related to daily commuting. A 2022 study found that particulate matter and black carbon aerosols peak in Houston during the morning commute. However, the clouds are too tethered to the roadways to justify the aerosol explanation. Mote agrees with me. “I think this is tied to the differential heating associated with the roads,” he said.

It will make for a fascinating urban climate study. Stay tuned.