Why doesn’t drizzle always show up on the radar? Here’s an explanation

Smaller water droplets and where they form could be to blame

Mist in Mico. Photo Sent in via KSAT Connect (Copyright 2023 by KSAT - All rights reserved.)

It’s a question we often get asked in the KSAT weather department: why is the drizzle at my house not on the radar?

There are a few reasons why drizzle might not be showing up when you check the radar. Here’s a breakdown:

1. The Water Droplets are Smaller

The water droplets that make up drizzle are typically a lot smaller than raindrops. Those smaller water droplets aren’t as easily detectible when the radar beam is searching for them in the lower levels of the atmosphere.

(For an in-depth explanation on how the radar works, check out this KSAT Explains episode!)

2. Drizzle May Form Below the Radar Beam

Drizzle also forms in the lower levels of the atmosphere. Because of this, those water droplets may be positioned below the radar beam when it’s scanning the sky. Thus, they go undetected and are not shown on the radar display.

An alternative method that meteorologists often use to detect drizzle and mist positioned below the radar beam is visibility.

For example, below is a look at visibility values from the lunch hour on Thursday, March 30. You can see where the drizzle and mist really settled in, especially in places like New Braunfels, Randolph AFB and Kerrville.

Visibility values due to drizzle and mist on Thursday, March 30, 2023 around San Antonio.

So the next time it’s drizzling at your house and you can’t find it on radar, those reasons may be why!

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About the Author:

Meteorologist Mia Montgomery joined the KSAT Weather Authority Team in September 2022. As a Floresville native, Mia grew up in the San Antonio area and always knew that she wanted to return home. She previously worked as a meteorologist at KBTX in Bryan-College Station and is a fourth-generation Aggie.