If you somehow haven’t seen it yet, the central plot of the 2024 blockbuster hit “Twisters” involves scientists in Oklahoma attempting to solve tornadoes. Their proposal, basically, is to deploy technology inside a tornado that could absorb the moisture of a storm and cut off its energy source.
But for their devices to work, our heroes first need to actually increase the amount of rain — you know, for plot reasons.
While the movie’s science is pretty flimsy, it is actually based on a very legitimate weather modification technique called cloud seeding.
In real life, scientists have been working on extracting extra precipitation from the clouds for nearly 80 years, although surprisingly few people seem to know about it.
Currently, cloud seeding is being used by more than 50 countries and by 11 states in the U.S. If you live in California, Colorado, Idaho, Kansas, Nevada, New Mexico, North Dakota, Oklahoma, Texas, Utah or Wyoming, it’s already happening where you live.
Although it may not look quite as dramatic as in the movies.
What is cloud seeding?
“Sometimes it's difficult to explain what cloud seeding really is because it impacts so many different areas and people do it in so many different ways,” says Katja Friedrich, a professor of Atmospheric and Oceanic Studies at the University of Colorado Boulder.
In Nevada, they need help with their drought. In Idaho, they mainly use it to produce water for hydropower. But in Texas, it’s mostly for irrigation.
In South America, Argentina uses cloud seeding to protect its vineyards. And in Alberta Canada, insurance companies sponsor cloud seeding programs to minimize hail damage to their homeowners’ roofs.
The goal of cloud seeding is simple: Scientists encourage water droplets to come together to form precipitation that is just large enough to drop out of the cloud.
And if we know that a huge hail storm is coming, we can attempt to form a lot more hail, but at much smaller and safer sizes.
How does cloud seeding work?
“What we're trying to do is just grow [droplets] big enough so that gravity can take over and they fall out,” Friedrich says. “And there are various mechanisms of how you can do this.”
One technique used in cloud seeding is to have exceptionally brave pilots fly directly into storm clouds and use flares to burn silver iodide off the wings of their planes.
(Silver iodide is also the substance used in the movie “Twisters” — in that case, it’s added to rockets that are shot up through the middle of the tornado. Dangerous!)
The water droplets in the storm cloud are supercooled, meaning their temperature is below water’s freezing point (0°C), and yet they’re still a liquid (not ice). So when we inject silver iodide, we effectively give those supercooled water droplets the ideal surface to cling to.
Cloud seeding scientists want these tiny supercooled water droplets to freeze into ice particles, which will stick to other ice particles and then fall out of the cloud as snow. (If it’s warm enough, the snow will turn into rain before it reaches Earth’s surface.)
These liquids are super unstable. If they get bumped, hit or poked at all, they will freeze instantaneously. So, pilots can “bump” the storm cloud with their plane to encourage the supercooled water droplets to freeze.
“Every time we get into an airplane and you fly through a cloud, you're doing cloud seeding,” Friedrich says.
Researchers can tell that resulting precipitation is from cloud seeding because the rain comes down to Earth in these bizarre, zigzag patterns rather than its usual lines or blobs — following the precise flight plan of the cloud seeding plane.
And there’s some new research by Prof. Linda Zou at Khalifa University in Abu Dhabi suggesting that a nanoparticle made from a sodium chloride core and a titanium dioxide surface could replace the silver iodide salt. Her raindrops are almost three times larger than regular raindrops, and therefore are much more likely to fall out of the cloud, and make it to Earth’s surface.
How did we discover cloud seeding?
The first person to successfully “seed” a cloud was Vincent Schaefer, an American chemist working for General Electric. Back in 1946, he was experimenting in the lab with his brand new freezer appliance.
He exhaled inside of it to see his breath, and then plopped some dry ice through his little cloud. Within the blue hazy fog, he observed the instant formation of millions of teeny tiny ice crystals.
Later on, he swapped out the dry ice for a really cold (−35°C) sewing needle, and learned that he could draw ice crystals into his cloud.
A few months later, Schaefer took his experiment to the sky, where he threw dry ice out of a moving airplane to see if he could generate precipitation. And it absolutely worked: “It seemed as though the cloud almost exploded,” he said.
Scientists like Friedrich refer to these early decades as the “Wild West” of cloud seeding. Nowadays, safety precautions have been implemented to upgrade Schaefer’s technique, but overall, the strategy has remained the same.
How much rain can we produce with cloud seeding?
Friedrich was part of a groundbreaking project in 2017, where for the first time in 80 years, scientists were able to quantify how much precipitation was produced after cloud seeding.
The goal of Friedrich’s Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE) was to understand how precipitation forms and evolves within a storm and to determine the role silver iodide plays in snow production.
For more than two months, Friedrich’s team monitored Idaho Power’s cloud seeding program in the Payette Mountains. Idaho Power, a hydropower company that supports southern Idaho and eastern Oregon, has been staunch supporters of the weather modification technique since 2003.
“No two clouds are alike, so in nature it's really difficult because once you change it, you don't have proof that this is really from seeding or whether the cloud is doing this already,” Friedrich explains.
Friedrich and her colleagues used radar and precipitation gauges to collect before-and-after data, which helped them build numerical models.
From their experiment, they determined that Idaho Power pulled enough snow out of the clouds in just over an hour to fill 235 Olympic-sized swimming pools with water.
“And that was very revolutionary when we published that, we were one of the first teams who could really show the entire chain of events,” Friedrich said. “You're putting the silver iodide in there. We can see this change and we can see the precipitation falling out.”
So can we use cloud seeding to battle tornados like in “Twisters”?
Hard no. It was an entertaining movie (and Glen Powell and Daisy Edgar Jones made meteorology look really good), but without giving away too many spoilers, that ending is pure science fiction… for now.
To learn more about cloud-seeding science, listen to the latest episode of the KCUR Studios podcast Seeking A Scientist.
Additional sources from Seeking A Scientist:
- Marvel’s Storm
- Evaluation of Wind Vectors
- Horizontal Wind Fields for Operational Weather Surveillance
- Weather vs. Climate
- Water Cycle
- Terrestrial Components of the Water Cycle
- Cloud Formation
- The Hydrologic Cycle
- Cirrus Clouds
- Stratus Clouds
- Cumulus Clouds
- National Geographic Education, The Cloud
- Hexagonal Shapes: Silver Iodide and Water
- Critical Issues in Weather Modification Research
- Common Questions and Answers about Cloud Seeding
- Project Skywater
- Cloud Seeding Wrongly Blamed for Flooding
- Environmental Impact of Using Silver Iodide As a Cloud Seeding Agent
- Human Impacts on the Environment
- Human-Caused Environmental Change
- Economic Impacts of Cloud Seeding on Agricultural Crops in North Dakota
- Feds Spend $2.4 Million on Cloud Seeding for Colorado River
- Operation Popeye
- Environmental Modification Convention Treaty
- Wisconsin State Legislature on Weather Modification
- Utah’s Snowpack and Reservoir Levels
- Can Cloud Seeding Stem the Water Crisis?
Seeking A Scientist is a production of KCUR Studios. It's made possible with support from the Stowers Institute for Medical Research, where scientists work to accelerate our understanding of human health and disease.
It's hosted by Dr. Kate Biberdorf, AKA Kate the Chemist. Our senior producer is Suzanne Hogan. Our editor is Mackenzie Martin. Our digital editor is Gabe Rosenberg.
This episode was mixed by Suzanne Hogan with support from Celia Morton, Byron Love and Genevieve DesMarteau.
Our original theme music is by The Coma Calling. Additional music from Blue Dot Sessions.
