Quality cloudy and overcast HDRI sky.
Download this great overcast sky HDRI Image pack for free. Included in this download is a 8000 x 4000 HDRI Image with BG and REF images.
Credit for this HDRI goes to HDR-VFX & HDRLabs.
Free sources are often enjoyable but not always at the same quality comparing a commercial stuff made by professionals. For that reason HDRI-Hubs main goal is to provide you with super high resolution hdri images and architectural textures.