air traffic

spotters on the ground

air pollution

Cars making the pollution that they are accustomed to using.

People getting out of their P.J.'s to go to work and check out the barometers.

I know the answer as I looked up this very question a few days ago. I've been noticing and have been commenting (quite vocally because who doesn't like to complain about the weather) that the person I have trusted for years to be fairly accurate with the forecast has been wrong a lot over the past few months. And now I know why.

Meteorologists going to work

No complaints about the weather where I live.

I agree with air pollution

Historically, they have predicted the movements of cold or warm fronts by tossing TP in the air and measuring the wind speed and direction. They have tried to do this with face masks, but they have proven to be less accurate. They are going to try using political yard signs next.

I'm going to guess, generically, the movement of people and animals.

well, I would think that airlines radio information, or use telemetry to share external readings with the ground. When is the last time you saw a meteorologist put an isobar on the screen?

pre 'rona ...