After reading a few articles about weather modification, and attending a Long Now seminar about the long term effects of geoengineering, I’ve decided to give it a try. It turns out that weather modification isn’t terribly difficult.

The most common method of weather modification is cloud seeding. Rain or snow can be caused by introducing lots of small particles into the sky. These particles act as gathering points for water vapor to form around. As the vapor condenses into liquid (or sublimates into ice) it is pulled down by gravity, creating precipitation.

The most popular “seed” for causing causing weather comes from Silver Nitrate, a hexagonal substance similar in shape to that of a snowflake. Another tested and proven cloud “seed” comes from dry ice vapor. For the purposes of this instructable, we will use dry ice as it is most easily found.

Step 1: Step One: Wait for the Right Moment

If you launch your balloon during optimal conditions it is possible that you may see better results. It is easier to pull rain out of a moist sky, especially if clouds have already formed. Information about humidity, cloud cover and cloud ceiling are available on websites such as http://www.aviationweather.gov/

Step 2: Step 2: Prepare the Balloon

Things to consider:

Dry ice sublimates (turns from solid to vapor) over time. We must use a piece of dry ice large enough that there will be some left when it reaches the cloud layer.
The balloon must be large enough to lift the dry ice.
The helium inside of the balloon will increase in volume (up to 4X the size) as it goes up in the atmosphere, so it is important to use a balloon large enough to avoid popping.

For the purposes of this experiment, a 36” balloon was used, and it was able to a 110 gram chunk of dry ice.

Step 3: Launch the Balloon

Once you have prepared the balloon, take it to a location free of overhead obstacles, wait for a cloud to pass overhead, and let it fly.

The dry ice will release gaseous CO2 particles, attracting water molecules, and possibly causing precipitation.

Step 4: Record and Publish Your Findings

The launch occurred at 4:49 on October 24, from San Francisco, CA 94107, at Latitude: 37.778103 | Longitude: -122.40271

At the time of the launch, the humidity was 79%, and the cloud ceiling was at 2,000 feet. There was zero precipitation before or after the launch. More research is required into the best practices around DIY Weather Modification. If you experiment with cloud seeding, please post a link to your documentation in the comments!