Artifact rejection

No, obviously rain isn't an artifact, but dust spots can be, compression artifacts such as JPEG compression, too much noise, both colour and luminance noise, so probably your image suffers from some of these issues.

Hi Chimperil,

It would be helpful if you upload to this thread a copy to the photos you want us to check for you.

Best wishes

JG

Rain is not artefact. But may be there is more than rain on your picture. Without the picture we cannot advise.