What does it mean for a man to send a rain and fog video on the road?

I want to tell you that he is in a bad mood.

The man sent a video of rain and fog on the road to tell you that he was in a bad mood, and expressed his mood at this time with gloomy and foggy weather.

When the other person is in a bad mood, you can change the topic to something happy, which will help to divert the other person's attention and help the other person relax.