What Is Virga? — In Plain Words

General information only.

The short answer

Virga is precipitation falling from a cloud that evaporates before it reaches the ground.

The National Weather Service Glossary puts it this way.

Virga is streaks or wisps of precipitation falling from a cloud but evaporating before reaching the ground.

So the rain or snow starts to fall.

Then it turns back into water vapor in the air.

None of it lands.

A note about the sources

The official weather sources explain virga briefly. The glossary entries are one or two sentences long. The explainer pages add only a few short passages. This page stays short for that reason. It does not add material from outside the official sources.

What virga looks like

The Weather Service pages describe virga as streaks or wisps under a cloud.

One Weather Service glossary describes it as wisps or streaks of rain falling out of a cloud but not reaching the ground.

That same glossary says that when the streaks are seen from a distance, they can be mistaken for funnels or tornadoes.

The Weather Service “Owlie’s Weird Weather” page describes what is left as feathery streaks extending from the cloud’s base.

That page says the streaks show the path the rain or ice took before becoming water vapor.

It also calls the streaks thin wisps of virga drifting through the sky.

Why it happens

The cause the official pages give is dry air below the cloud.

The “Owlie’s Weird Weather” page says that when the air beneath a cloud is very dry, precipitation falling through it evaporates before reaching Earth’s surface.

The Weather Service Downbursts page says the same thing in shorter words.

It says the atmosphere below the clouds tends to be very dry, and rainfall evaporates before it touches the ground.

A Weather Service radar explainer page says that if you have a dry air mass in place in the low levels, sometimes rain cannot completely penetrate that dry layer before it evaporates.

That page adds that the deeper into the dry air mass you go, the less chance the rain has of reaching the ground.

What the evaporation can do

The official pages state a few effects.

Each one below is tied to the page that states it.

Cooling. The “Owlie’s Weird Weather” page says the evaporation process takes a lot of energy out of the surrounding air and causes it to cool.

Sinking air and gusty winds. The Weather Service Downbursts page says this cools the air and increases the air’s density, with gravity pulling the dense air toward the surface.

That page says gusty winds occur in the area of the virga.

A microburst, in certain cases. The National Weather Service Glossary says that in certain cases, shafts of virga may precede a microburst.

The “Owlie’s Weird Weather” page says the cooled air may then sink very quickly and dump a dangerously concentrated parcel of air and water or hail in a microburst.

That same page also says that, for the most part, virga is a visual effect.

Why radar can show rain when nothing reaches the ground

Radar can detect the precipitation while it is still in the air.

The Weather Service radar explainer page says the radar will still detect the rain aloft, but you may not see it at the surface.

It says the radar is not lying.

The rain or snow is simply not hitting the ground.

The “Owlie’s Weird Weather” page says virga shows up on radar as a typical rain or snow shower, but there is no evidence of that at the surface.

The radar explainer page adds one more point.

It says this is one reason why it is hard to break drought conditions once they set in.

Rain that you do get is reduced because of the dry air in place.

Where it is commonly seen

The “Owlie’s Weird Weather” page says virga is commonly seen in the Western U.S., desert climates, and other dry areas.

That is the one place statement the official pages used here make.

This page does not add other places.

General information only.