Why does the temperature plummet at night in the desert?

Question

But here in britain if it's been hot in the day it stays hot in the night?

Answer 1

low humidity.

Humidity is water in the air.  Water in the air is a greenhouse gas, which keeps the area warm at night and there is less of that effect in the desert due to the smaller amounts of moisture in the air.

Answer 2

There is generally no cloud cover and the heat at the surface is allowed to reradiate away from the earth's crust..

Answer 3

As we're an island, as the sun heats up the ground it also heats up the surrounding sea. When the sun goes down and the temperature starts to drop, the temperature ot the sea goes down too but not at the same rate as land. In effect the sea is keeping us warm.

In the desert, the reason for massive temperature differences is the sun bakes the ground (which doesn't take that much energy to heat up in comparison with water). When the sun goes down the ground gives this heat back rapidly causing the drop in temperature.

This effect can also be seen in places like Siberia where the temperature differences between night and day are drastic. In short islands or coastal regions tend to have a smaller difference in day/night temperatures because of the sea, and inland places (deserts, Siberia, central United States) have  more harsher nights.

Hope this helps answer your question.