does warm air weigh more than cold air?
344631
As far as the weight is concerned they are same.  But in a constant volume situation yes the hot air would weigh less then the cold air.  Hot air expands and therefore rises up in the atmosphere.
214499
It all has to do with altitude. The higher you are from the earth, the colder it gets. Air is also thinner.
683535
No. \nHeat will flow from an object that has more temperature to another with less temperature. An object having less temperature can have more thermal energy than another witj more temperature. This will depend on the mass of the object. See it this way: 1 gram of iron at 1000ºC has less energy than 1 ton of iron at 100ºC. Heat will flow from the object with less energy to the object with more energy in this case. But it will always flow from the object with more temperature.
194124
Because the air spreads out, and as it spreads out it retains less heat.\n\nAnd while cold air does sink and hot air rises, as cold air does get lower in altitude it warms up, and hot air cools as it rises. \n\nI live in the foothills west of Denver so I see the rising/falling air thing firsthand. In the winter we get this air that 50 miles to the west was part of a blizzard. As it descends the mountains, it dries out and heats up sometimes bringing temperatures in the middle of the winter into the 60's or 70's.
49934
It depends.  Usually you will have the cooling effect as mentioned by the previous answer to to rarifaction of the air, but there's also the fact that the air being thinner leads to the top being more sensitive to changes, and the sunlight is less filtered.  The sun will feel hotter at high altitudes, and the last time I drove over Tejon Pass (which connects LA to the San Joaquin Valley), I noticed that the temperature rose as I ascended.  That same weekend, I check the weather report on the Kirkwood (ski resort) website, and they referred to an inversion, where the temperature gets higher as you go up.  I also know that at time camping in the mountains in the height of summer, it can be much hotter in the mountains than at sea level.\n\nDeserts are likewise often miisunderstood.  Generally we think of them as hot, but they can also get extremely cold because there's no moisture in the air to hold heat.  Some of the biggest deserts are in Antarctica.
587432
Colder air is "thicker," moves much more slowly than does hot air, and is heavier than warmer air...Air will set up a gradient from the coldest at the bottom to the hottest at the top in a container...
367999
It weighs the amount that the air inside it weighs.
417406
Cold falls, right! The higher you are in altitude, the colder it gets!
804973
A fundamental axiom: cold air is heavier than warm air.\n\nThus, cold air sinks (like into a valley) and hot air rises.\n\nHowever, the temperature gradient (how temperature changes with increasing altitude) is negative.  This means air gets colder as altitude increases.  So what we have is cold air at altitude pushing down on warm air near ground level.\n\nThe warm air heat comes from the ground, which is heated by our Sun.  In summer, there is a lot more of that solar energy to heat the ground and lower air in the valley than in winter.  Thus, the valley air is warm.  In fact, the weight of the colder upper air contributes a little bit to the heat below because a gas under pressure does heat up.  But in winter, when there is far less solar energy and resulting heat, the naturally colder air above settles into the valley.  \n\nBoth the cold and warm air are more or less trapped in the valley because of the hills or mountains surrounding it.  Thus, the cold air stays colder because no warm air is blown from the surroundings into the valley.  And the warm air stays warmer because no cold air is blown into it.
554015
The common answer to this question for a hot air balloon is "hot air is lighter than cold air." What does this really mean?\nIt means that hot air is less dense than cold air. Remember that density equals mass divided by volume. The substance with a lower density will float on top of another with a greater density. When the air inside a hot air balloon is heated, molecular motion increases, and the volume of the balloon expands. Therefore, its density decreases. The balloon will float until the density of its gas equals the density of the surrounding air. The density of the air decreases as altitude increases; because of gravity; gas molecules are more sparse at higher elevations. The air is "thinner" at high altitudes. The pilot can increase his altitude by heating the gas inside the balloon, thus decreasing its density.
32289
One answer would be to convert 0C into 273 Kelvin or 32 F and then do some multiplication.\n\nBut "cold" is really a subjective measure based on physiology. I suspect if you did a test with actual humans you would find that around -10.6 C feels twice as cold as 0 C.\n\nThat is what this wind chill calculator finds, if wind speed is always zero.
586003
Air Pressure.  The humidity and such in the air is higher and therefore holds more warmth.\n\nAt higher altitudes, where the air is less dense, there is greater distance between particulates and heat is lost faster.
139400
the air gets thinner as you rise in elevation.  the thin mountain air doesn't trap the heat as well as the thick air near sea level does.
556156
If it's non heated, it's going to be the temperature of the surrounding air and ground.
900354
Because hot air rises and cold air sinks - it's heavier and hense will be found more at ground level.
924970
Atmospheric Pressure VS Vacuum -- which is stronger?
811649
You may be right.  The force that they respond to is gravity.  Cold air, being denser, will, in a fluid medium, be drawn closer to the earth, displacing warmer, less dense air.