The Science Mouse

Desert, courtesy wikipedia

A desert is a unique biome that receives less than ten inches of rain a year.  Deserts are very dry, but they are not always hot.  There are two kinds of deserts: hot deserts and cold deserts.  The hot desert is the kind of desert we are most familiar with.  They can be very hot.  The Sahara Desert reaches daily temperatures over 110 degrees Fahrenheit regularly during the summer.  The hottest temperature every recorded on earth was in the Sahara:  136 degrees Fahrenheit.  That is very hot!  But even hot deserts are not always hot.  At night, temperatures can drop to 41 degrees Fahrenheit, even after reaching temperatures over 100.  During the winter, nighttime temperatures can drop below freezing.

Why do hot deserts get so cold at night?  Deserts are very dry.  Moisture in the air acts like a blanket and insulates the ground, keeping the heat in.  Since there is little moisture in the air in a desert, the heat escapes as soon as the sun goes down.  This is a special challenge to plants and animals because they have to have adaptations for surviving the cold of night and the heat of day.

Antarctica , courtesy wikipedia

Cold deserts are found in Antarctica, Greenland and near the arctic zones.  Winter temperatures average between 28 degrees Fahrenheit and 3o degrees.  Summer temperatures may reach 78 degrees.  They can actually get quite a bit of precipitation, usually as snowfall in the winter.  The soil is porous, which means it has lots of holes.  Water drains off the surface very quickly, so the soil is dry even after heavy rains or snow melts