Question: Can you tell me how the weather would be different at 500 millibars?

Answer: Millibars is a unit of atmospheric pressure, with the normal value near sea level around 1013. Air pressure decreases with increasing altitude, and drops to 500 millibars at around 18,000 feet above sea level. At that height, temperatures often range between about -15 and +15 degrees F, winds sometimes exceed 100 mph, and air density is a little under 60 percent of that near sea level.