is it true?

Question

one of my teachers said in the desert at night if its 60 degrees you have to wear a winter coat because it feels a lot colder, is this true

i just can't imagine 60 degrees feeling cold even if it was 90 degrees during the day

in phoenix it is in the 80's for a low temperature in the summer, does this feel cold too?

Answer 1

The reason it becomes so hot during day and chilly at night in the desert is because sand grains have alot of air space between them and water tends to filter thru them - compared with clay soil for example which has little air space and tends to remain moist. Thus the sand surface is primarily heated in a very shallow layer and becomes hot rather than the heat being conducted much further down (notice how hot beach sand is at midday for example). Likewise, it cools much more efficiently at night.

A consequence of that is the ground temperature may be much lower during a calm night than the temperature at 2 meters which is reported. Your body is almost if not entirely below the level air temperature is measured at - does not make a great difference, but some.

Deserts tend to be dry. Although the heat index is only mentioned when it's warm & humid, the fact is that even if it is not humid there still is some difference in the comfort level with a dewpoint of 55° and one of 20°, for example. The drier the air, the more evaporation from your skin, which cools it.

Combine those and you can see why - though the temperature is simply a measure of the kinetic energy of the molecules in the air - which does not differ because of humidity or where you are. The only thing which does make a difference is air density. I.e., if there are not *as many* molecules traveling at that root-mean-square speed which we call 60°, not as many hit you and you feel cooler. Thus it is correct to say that 60° on a mountain top feels cooler than 60° at sea level below it.

During a nice night lay or sit down with no coat for an hour or more when it is around 60° and I'll bet you'll feel cold. It's just that when you are walking or doing other activities it keeps your body warmer.

A couple common misconceptions are that the air holds water vapor and/or the water vapor (humidity) holds heat. I cannot say that the dry air & water vapor molucles are exactly the same temperature (radiative properties differ to some extent, and water vapor may actually cool quicker at night), but can say dry air & water vapor co-exist in the atmosphere as gases and thus neither "holds" the other.

Answer 2

Because the Atmosphere in desert areas contains very little moisture the air temperature at night can really plummet down to a point where it feels cold out. This may not be so during the hottest parts of the summer but it will feel cool.

Answer 3

Yes, deserts can get quite cold at night. This is due to lack of humidity. Humidity - moisture in the air - holds heat. Since deserts are so dry, the air doesn't hold much heat and they cool very quickly when the sun goes down. Heat pumps (vs. conventional home air conditioners) work on this principle.
It also affects the heat index (how hot it feels when temperature and humidity are combined). For instance, one evening in Las Vegas NV, the temperature was 101 F, but the heat index was 95 F - because it's so dry it felt cooler. Right now in Tampa FL, the temperature is 87 F, but it feels like 95 F - because it's so humid it feels hotter.

Answer 4

Yes, 60 degrees in the desert feels like winter. It's a big drop for at night time.. You definitley need at least a sweater or sweatshirt and long pant and socks. And in the daytime people with pools don't use them much because the water get too hot. It's not refreshing at all.

Answer 5

right, I'm in Manila right now and 85 degs feels about 100! its due to humidity. Same in opposite for desert. 60 degs will feel colder in low humidity desert conditions relative to normal.
rock on

Answer 6

That is true. I'm from West Texas and you can experience the same phenomenon there. It has to do with the moisture in the air. Since the desert (and west texas) are arid, there is not much moisture in the air to hold onto heat.

Answer 7

Yes. The change from the heat of day to the cold at night is lethal.

Answer 8

In the desert its deadly hot during the day and at night its deadly cold!

Answer 9

Yes, it's true. I didn't believe it when I went to Egypt. We were going to be out until night, so we were told to bring sweaters. It was very hot, so I didn't. As night came, my bones were hurting so much because it suddenly got so cold, and I din't have anything to keep warm.

It's true!

Answer 10

Yes it is true.