It appears there are dark ominous cloud headed in your direction. You may head inside and prepare for the rain to start falling, but strangely, there's no rain touching the surface. You may look at the radar and find that its showing precipitation.
This could be a common situation that occurs when there is Virga from rain clouds. Virga is precipitation that falls from a cloud but evaporates before hitting the surface. It will show up on radar, because there is precipitation within the clouds. It's just not making it way to meet us at the ground level. This is because of a dry air mass that is cutting of its supply of saturated air causing it to evaporate as the precipitation is falling. If you find yourself in the situation above, look up at the clouds. Virga leaves a wispy look underneath the base clouds, which is the precipitation that is falling and evaporate as it falls. Some common rain clouds Virga be associated with are; Cumulonimbus, Cumulus, Cirrocumulus, AltoCumulous, Stratocumulus, and Nimbostratus.