Clearly it's not raining at the moment. This is a good example of "ground clutter".
Echoes from objects like buildings and hills appear in almost all radar reflectivity images. This "ground clutter" generally appears within a radius of 25 miles of the radar as a roughly circular region with a random pattern. An mathematical algorithm can be applied to the radar data to remove echoes where the echo intensity changes rapidly in an unrealistic fashion.
But as you can see, sometimes it's more fun to leave the clutter in. Life with clutter can be fun.