Occasionally radar images will display features that aren't meteorological in nature. This can be due to animals like bugs and migrating birds, orthographic features such as a mountain range, or even the atmosphere itself! Here are some examples of interference you may see and suggested causes of each.

Sometimes you will see outward lines radiating away from a radar station. In this image, you can see the CASET radar station showing three outward lines to the north, west, and south. In some instances, you will see this during a sunrise or sunset, when the sun is at the exact angle the radar beam is measuring. However, the image above was captured at night. Instead, there are other things that can affect the radar instrument. Typical causes include radio interference, similar to static you'll hear on a radio. For instance WiFi networks are on a similar frequency band as weather radar. If a mis-configured WiFi network is strong enough, it can overload a scan in its direction from the radar. Taller buildings could block or reflect a radar beam in an unexpected way.

Sometimes you'll notice a radar image showing almost a “glow” of rain just around a radar station. The radar might show that it is raining in your area, even though it's clear outside. It's most common in the summer time in the evening hours. In this case, what you are seeing is ground clutter. In the example above, in summer months, there's a good chance you are seeing bugs like mosquitoes being picked up by the radar station. But you can also notice bird migrations and other ground-based clutter. Sometimes this clutter can be filtered out of the image, but that's not always the case.

Occasionally the atmosphere itself can cause ground clutter. If the atmospheric conditions are just right, the beam can be reflected back to the ground by a layer of air with a quick temperature change. This is similar to the waviness you might notice at a sunset over a large body of water. When the beam is reflected, the radar instrument will see the ground (where the beam is being reflected) instead of precipitation, and this could show up on a radar image.