Question: why do rainbows only apper when it rains?

Lauren Mc Keown answered on 14 Nov 2013:

Good question Joanna! It’s because the tiny water droplets in our atmosphere which occur when it rains act as prisms which split white light from our Sun into the colours which make it up! You might also see rainbows on a sunny day near fountains and things like that for this reason 🙂