Some radar returns may appear in areas where no precipitation is expected nor are conditions consistent with such a return (e.g., no clouds). If you are in the area in question, a visual confirmation of the area may substantiate the returns as being false. The picture below shows an example:
Image 1. Sample false radar return.
This type of non-precipitation return can be due to stationary objects on the ground such as a wind turbine farm in the area. Wind turbine clutter is a common occurrence at multiple locations throughout the country where the farm is close to the radar site. It occurs most frequently at night and early mornings when the side lobes of the radar get ducted toward the earth. They are a nuisance when it comes to ground-based radar system and they may not be easily filtered out especially when there's real precipitation nearby. The best we can do in some cases is to recognize the characteristics of non-precipitation returns. One strategy is to loop the radar image. If the returns tend to stay anchored over a fixed position this likely means they are non-precipitation returns.