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Precipitation Simulator

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Make it rain and snow in this precipitation simulator! Set the air temperature (green) and dew point (yellow) in the four different altitudes and see what type of precipitation will fall to the ground. Watch closely. They may even change form as they fall. After you're done simulating a rainstorm or a snowstorm, scroll down to learn more about dew points!

You must use an up-to-date browser version to view this!

Legend of symbols:

snowflake/ice crystal
supercooled droplet
snow grains
freezing rain or drizzle (on ground)

“Precipitation Type" WebApp Courtesy of the Cooperative Institute for Meteorological Satellite Studies (CIMSS), Copyright © 2013 by Tom Whittaker at the University of Wisconsin-Madison.

What's Dew Point?

Moisture measured in degrees? What?

The dew point is the measure of how much moisture is in the air. The higher the number, the more moisture there is. But you may notice that it’s measured in degrees Celsius. Why would a unit of water in the air be written in a temperature scale?

The number on this simulation is the dew point temperature. This is the temperature at which the air can’t hold any more water vapor. When the temperature of the air cools to the dew point, water vapor condenses into liquid water.

The dew point will always either be the same or lower than the actual, or ambient, temperature. Think of the dew point temperature as the goal temperature for condensation to happen. It isn’t the actual temperature of something we’re measuring. Instead, it’s marking the temperature line where water vapor is going to condense and lead to rain, snow, hail, and other forms of precipitation.

What this all means is that when you move the green and yellow lines in this simulation, you’re actually determining the relative humidity (RH)—how much water is in the air. If you place them in the same place, that gives you 100% humidity. See how that affects the type of precipitation. If you move the yellow and green lines far apart, you’re setting the humidity level very low. If it’s extremely low, there might not even be a cloud in the sky.

Can you move around the points on the simulation above to get all the types of precipitation?

up close photo of a snowflake

When you’re done, click here to try your skills at building snow crystals!