Why is Neptune so windy? On earth here I once heard the average wind speed on ground level is approx. 20 miles an hour. I’m sure this varies. But why is neptunes windspeed upwards of 1k miles per hour?
Neptune has a very fast rotation.
It’s also windy because of close proximity to Uranus. 
Generally, the colder the planet, the faster the winds.
The explanation I read was that without convection processes (up and down drafts) caused by solar or geothermal heating sources, the less disturbance. And with less disturbances, the winds can pick up momentum.
Peace.
You could have just taken me to the pit if you wanted to get all personal abou it… 