There is always some moisture in the air, even if it is not always
visible. When the air temperature begin to drop, and is unable to hold
any more moisture this is when tiny drops of water start to appear.
This is what is generally known as condensation. Some examples are
when you see your breath on a cold day, or when the mirror mists over
when you are taking a bath or having a shower.
Condensation occurs mainly during cold weather, whether it is raining
or dry. It will usually appear on cold surfaces or in places where
there is little or no movement of air. Try looking for evidence of
condensation in corners, or on our around windows, may at the back of
wardrobes and cupboards.
It is very often found forming on