In the early days when "radar" technology had just emerged, clouds, fog, rain, and haze all caused a certain degree of echo interference to radars. The electromagnetic waves emitted by the radar would be partially reflected, absorbed, or scattered by these elements, resulting in unstable results.
However, as technology progressed, radars became more precise, their emissions often confined to a very narrow band of frequencies, and interference could be filtered out through modulation techniques.
By the 21st century, apart from a small amount of meteorological radars that deliberately confined electromagnetic waves to specific bands, most radars were not affected by cloud and fog interference.
However, the essence of "fog" is water droplet aerosols that use air as a dispersant. If these "particles" were replaced with metal flakes, then the situation would be quite different.