Drizzle, Showers, Downpours and Cloudbursts: What’s the Difference

Some rain barely seems to count. Other rain can turn a street into a stream in minutes.

We use words like drizzle, showers, steady rain, downpour and cloudburst casually, but they don't all describe the same kind of weather. Meteorologists distinguish different types of rain by characteristics such as droplet size, intensity, duration and the clouds and weather systems producing them.

And surprisingly, the amount of rain that eventually ends up on the ground is only part of the story.

What Is Drizzle?

Drizzle is made up of exceptionally small water droplets, generally less than about 0.5 millimeters in diameter.

Because the droplets are so small, they fall slowly and can seem almost suspended in the air. Drizzle commonly comes from low, uniform stratus clouds and may continue for hours without producing much measurable rainfall. It can certainly get you wet, though. Thousands of tiny droplets can coat plants, pavement and clothing even when rainfall accumulation remains quite small.

Fog and drizzle are closely related, too. In very simple terms, fog consists of tiny water droplets suspended near the ground, while drizzle droplets are large enough to fall.

What Is Steady Rain?

Steady rain is what many of us picture as an all-day rainy day: relatively consistent rainfall that lasts for an extended period rather than repeatedly starting and stopping. It is often associated with broad weather systems and layered clouds such as nimbostratus.

The rainfall may be light, moderate or occasionally heavy, but its defining characteristic is its persistence. Instead of arriving suddenly, it tends to cover a large area and continue for hours.

A long period of moderate rain can therefore produce considerably more total rainfall than a brief, dramatic downpour.

What Makes a Shower a Shower?

A rain shower isn't necessarily light.

The word shower describes the character of the precipitation more than its intensity. Showers typically begin and end relatively abruptly, vary in intensity and come from convective clouds.

One minute it may be dry, the next it may be raining hard, and 15 minutes later the sun may be out again. That's why a forecast for "showers" doesn't necessarily mean you'll experience gentle rain all afternoon. One location might receive a quick soaking while another a few miles away gets very little—or nothing at all.

Even within a neighborhood, rainfall can vary when small, localized showers pass overhead. Rainfall can differ surprisingly much across very short distances, particularly when scattered showers and thunderstorms are involved.

What Is a Downpour?

A downpour is simply a period of very heavy rain, usually occurring over a relatively short period.

Unlike terms such as drizzle, downpour doesn't have one universally used meteorological definition based on a particular droplet size or rainfall rate. It's a descriptive term for rain falling hard enough that visibility may decrease, water quickly collects on roads and roofs pour water from their gutters.

A downpour might last only a few minutes, but it can deliver a surprising amount of water. This is where rainfall rate becomes important.

If one inch of rain falls over 12 hours, the average rainfall rate is only about 0.08 inch per hour. If that same inch falls in 20 minutes, the average rate is about 3 inches per hour.

That difference between total rainfall and how quickly it arrives is called rainfall intensity, and it can have a major effect on what happens once the water reaches the ground.

What Is a Cloudburst?

A cloudburst is an exceptionally intense, localized burst of rainfall.

The term is most often used for extreme rain that falls over a small area in a short amount of time. Definitions vary, so there isn't a single rainfall threshold universally used to declare something a cloudburst.

What distinguishes one is the extraordinary intensity. During extreme rainfall, water can fall faster than the ground can absorb it or drainage systems can carry it away. Flash flooding, erosion and rapidly rising streams can result even when the storm itself doesn't last very long.

Despite the name, a cloud doesn't actually "burst." The rain is produced by powerful atmospheric processes capable of concentrating enormous amounts of water into a relatively small area.

Why Rainfall Intensity Matters

Plants and soil don't experience every inch of rain equally.

Gentle or moderate rain that falls over several hours has more time to soak into the soil. A very intense downpour may deliver the same total amount of water but overwhelm the soil's ability to absorb it.

Once rainfall arrives faster than the ground can take it in, more water begins running across the surface. Slopes, compacted soil and already-saturated ground can make runoff even worse. That's one reason rain can affect soil health differently depending on how and when it falls.

That's why "we got an inch of rain" doesn't always tell the whole story. How quickly that inch fell can matter just as much as how much fell.

Why Raindrops Aren't All the Same Size

Even within a single storm, raindrops come in many sizes.

Tiny cloud droplets collide and combine as they move through a cloud, eventually becoming large enough to fall. On their journey toward the ground, drops may continue colliding with other drops, evaporate partly in drier air or break apart. A surprising amount can happen to a raindrop between the cloud and the ground.

Small raindrops are nearly spherical. As drops become larger, air resistance flattens their bottoms, giving them more of a hamburger-bun shape rather than the familiar teardrop shape often used in drawings.

If a drop becomes too large, aerodynamic forces can cause it to break into smaller drops. The size of a raindrop affects both its shape and how fast it falls.

So a heavy downpour isn't simply a cloud filled with gigantic raindrops. It contains enormous numbers of drops of different sizes falling at different speeds.

The Same Storm Doesn't Produce the Same Rain Everywhere

Rainfall can vary remarkably over short distances, particularly with showers and thunderstorms.

One part of town can experience a soaking downpour while another remains nearly dry. Sometimes rainfall can even differ noticeably from one side of a large property to another, especially during small, highly localized summer showers.

Terrain, wind, storm movement and the structure of individual storm cells all influence where rain actually reaches the ground.

It's one reason rainfall reports from an airport or weather station several miles away don't necessarily describe exactly what happened in your backyard. Your rain gauge and your weather app may therefore show different rainfall totals without either one necessarily being wrong.

From Misty Drizzle to a Summer Deluge

Rain isn't simply water falling from the sky at different speeds. The clouds producing it, the size and number of droplets, how long it lasts and how quickly the water reaches the ground all shape the kind of rain we experience.

A gray afternoon of drizzle, six hours of steady spring rain and a ten-minute summer downpour can leave completely different amounts of water behind—and have very different effects on gardens, streams, roads and soil.

The next time rain starts falling, there's more to notice than whether it's raining. Sometimes the interesting part is how it's raining.