Does Illinois have a high altitude or low altitude?

That's a trick question, since at VERY high altitudes the trend reverses momentarilly. It's dependant on what the sun can heat: at low altitudes, where the atmosphere is predominantly oxygen and...

cumulonimbus clouds are at low, medium, and high altitudes while others are imbetween such as fog which is at the bottom of the low altitude.

The temperature is low at high altitude because air becomes thin when it reaches top. heavier air holds more moisture and makes it thick and allows it not to go to the top. Hence the fall in...

The air pressure at low altitudes is greatest due to the force of Earth's gravitational pull on the atmospheric gases. The air closest to the center of the Earth is pulled more by gravity and is thus...

it is faster at a higher altitude because there are less air pressure when you're away from the Earth. There are more air pressure as you come to Earth so it becomes slower.